A275478 Least k such that d(n) divides d(n+2^k) (d = A000005).

0, 0, 1, 3, 0, 1, 0, 1, 4, 2, 0, 3, 0, 0, 7, 5, 0, 1, 0, 3, 0, 1, 0, 4, 7, 0, 3, 2, 0, 8, 0, 6, 0, 0, 2, 6, 0, 0, 0, 1, 0, 7, 0, 0, 23, 3, 0, 5, 0, 1, 2, 3, 0, 1, 0, 5, 0, 1, 0, 9, 0, 2, 9, 7, 0, 2, 0, 2, 0, 3, 0, 7, 0, 2, 0, 3, 0, 5, 0, 5, 178, 1, 0, 8, 0, 0, 0, 4, 0, 24, 1, 2, 0, 0, 0, 6, 0, 0, 20, 9

Offset

1,4

Comments

a(225) > 300, if it exists. - Antti Karttunen, Jun 13 2023

Links

Antti Karttunen, Table of n, a(n) for n = 1..224

Formula

a(A057922(n)) = 0. - Michel Marcus, Aug 01 2016

Example

a(45) = 23 because A000005(45) = 6 divides A000005(45+2^23) = 18.

Mathematica

A275478[n_]:=Module[{d=DivisorSigma[0, n], k=-1}, While[!Divisible[DivisorSigma[0, n+2^++k], d]]; k]; Array[A275478, 50] (* Paolo Xausa, Aug 13 2023 *)

Prog

(PARI) a(n) = {my(k = 0); while(numdiv(n+2^k) % numdiv(n) != 0, k++); k; }

Crossrefs

Cf. A000005, A057922, A275473, A275479.

Sequence in context: A363946 A354824 A183700 * A248678 A325268 A232630

Adjacent sequences: A275475 A275476 A275477 * A275479 A275480 A275481

Keyword

nonn

Author

Altug Alkan, Jul 29 2016

Extensions

Data section extended up to a(100) by Antti Karttunen, Mar 02 2023

Status

approved