A352256 a(n) is the least k such that A033273(k) is equal to (A033273(n*k + 1) - 1)/n where A033273(n) is the number of nonprime divisors of n.

3, 13, 5, 41, 11, 2479, 23, 73, 103, 2249, 19, 7177, 211, 691, 3089, 1289, 53263, 726493, 41, 1597, 2243, 64406, 13129, 31351, 983, 1579, 197, 43037, 1411, 38246575, 389, 3607, 15403, 61286, 709, 1638349, 3587, 16249, 3585641, 1017119, 1292839, 132347, 593, 32203, 51963

Offset

1,1

Links

Table of n, a(n) for n=1..45.

Example

a(2) = 13 because A033273(13) = (A033273(2*13 + 1) - 1)/2 = (A033273(27) - 1)/2 = 1.

Mathematica

f[n_] := DivisorSigma[0, n] - PrimeNu[n]; a[n_] := Module[{k = 2}, While[f[k] != (f[n*k + 1] - 1)/n, k++]; k]; Array[a, 29] (* Amiram Eldar, Mar 10 2022 *)

Prog

(PARI) f(n) = numdiv(n) - omega(n); \\ A033273
a(n) = my(k=2); while (f(k) != (f(n*k + 1) - 1)/n, k++); k; \\ Michel Marcus, Mar 10 2022

Crossrefs

Cf. A000005, A001221, A033273, A350516.

Sequence in context: A331806 A331807 A084738 * A073580 A340349 A326609

Adjacent sequences: A352253 A352254 A352255 * A352257 A352258 A352259

Keyword

nonn

Author

Juri-Stepan Gerasimov, Mar 09 2022

Status

approved