matematik:oeis

On-Line Encyclopedia of Integer Sequences

Jeg vil måske lave en DVD med OEIS. Flyingant skal være på dvd'en.

Sekvenser med 2,3 eller 4 forskellige værdier. Nogle af dem kunne være interessante grafiske.

Forskellige værdier	Kandidater	Gode
2	A000480, A000484, A000494, A001468, A002819, A002909, A002928, A002930, A003589, A003687, A003782, A003842, A003849, A003982, A004539, A004547, A004555, A004569, A004593, A004601, A004609, A004641, A005171, A005369, A005614, A005713, A006337, A006338, A006340, A006345, A006461, A006466, A006513, A006836, A006928, A007061, A007362, A007421, A007424, A007538, A008683, A008869, A008870, A008966, A009058, A010051, A010052, A010054, A010055, A010056, A010057, A010058, A010059, A010060	A000002, A001030, A001285, A284680
3	A005678, A005679, A005680, A006460, A007413, A007423, A007540, A007706, A007877, A007945, A007968, A008741, A008868, A009501, A009529, A010121, A010122, A010130, A010133, A010141, A010143, A010152, A010153, A010170, A010194, A010195, A010227, A010331, A010872, A010882, A011187, A011770, A011771	A001176, A003137, A003270, A004530, A004540, A004548, A004556, A004570, A004578, A004586, A004594, A004602, A004610
4		A005681

Sekvenser, som jeg har bidraget til:

A030101 a(n) is the number produced when n is converted to binary digits, the binary digits are reversed and then converted back into a decimal number.
A055748 A chaotic cousin of the Hofstadter-Conway sequence
A247820 Numbers n such that sigma(2n-1) is a prime p.
A246910 Numbers n such that sigma(n+sigma(n)) = 3*sigma(n).
A265650 Removing the first occurrence of 1, 2, 3, … reproduces the sequence itself. Each run of consecutive removed terms is separated from the next one by a term a(k) ⇐ a(k-1) such that floor(sqrt(a(k))) equals the length of the run.
A160029 Primes of the form 2^(2^n)+51.
A169595 Primes p such that sigma(p+2)=sigma(p-2).
A169596 Primes p such that sigma(p+3)=sigma(p-3).

Interessante sekvenser

A001228 Orders of sporadic simple groups
A003001 Smallest number of multiplicative persistence n
A005132 Recaman sequence
A005150 Look-and-Say
A005602 Smallest prime beginning a complete Cunningham chain of length n (of the first kind)
A005845 Lucas pseudoprime
A006945 Smallest odd number that requires n Miller-Rabin primality tests
https://oeis.org/A008284/A008284 Triangle of partition numbers
A014577 Regular paperfolding sequence
A030101 Converted to binary digits, reversed and converted back into a number.
A036057 Friedman numbers: can be written in a nontrivial way using their digits and the operations + - * / ^ and concatenation of digits (but not of results).
A038219 Ehrenfeucht–Mycielski sequence
A036236 Smallest integer k > 0 such that 2^k mod k = n, or 0 if no such k exists.
A045911 Neither a cube nor the sum of a nonnegative cube and a prime.
A055748 A chaotic cousin of the Hofstadter-Conway sequence
A090822 Gijswijt's sequence
A096555 RANDU
A114440 Numbers which divided by the sum of their digits (Harshad or Niven numbers) give integers which are also divided by the sum of their digits (until a single digit Harshad remains).
A119566 Periodic table of elements associated with the Look-and-Say sequence
A121977 Numbers with a distinct frequency for each decimal digit.
A131884 Numbers conjectured to have an infinite, aperiodic, aliquot sequence.
A134204 Leroy Quet's prime-generating recurrence.
A179243 Numbers n that have three terms in their Zeckendorf representation.