A141377 a(n) = the smallest positive integer non-coprime to both n and d(n), where d(n) is the number of divisors of n.

2, 6, 6, 10, 2, 14, 2, 3, 2, 22, 2, 26, 2, 6, 10, 34, 2, 38, 2, 6, 2, 46, 2, 15, 2, 6, 2, 58, 2, 62, 2, 6, 2, 10, 3, 74, 2, 6, 2, 82, 2, 86, 2, 3, 2, 94, 2, 21, 2, 6, 2, 106, 2, 10, 2, 6, 2, 118, 2, 122, 2, 3, 14, 10, 2, 134, 2, 6, 2, 142, 2, 146, 2, 3, 2, 14, 2, 158, 2, 15, 2, 166, 2, 10, 2, 6

Offset

2,1

Links

Antti Karttunen, Table of n, a(n) for n = 2..16385

Formula

a(n) = A141327(n, A000005(n)).

Mathematica

a[n_]:=Module[{i=1}, Until[!CoprimeQ[n, i]&&!CoprimeQ[i, DivisorSigma[0, n]], i++]; i]; Array[a, 86, 2] (* James C. McMahon, Jul 24 2025 *)

Prog

(PARI) A141377(n) = { my(d=numdiv(n)); for(k=2, oo, if(gcd(k, n)>1 && gcd(k, d)>1, return(k))); }; \\ Antti Karttunen, Feb 18 2023

Crossrefs

Cf. A141327, A141378, A141379.

Sequence in context: A372610 A021978 A390981 * A006955 A306745 A196053

Adjacent sequences: A141374 A141375 A141376 * A141378 A141379 A141380

Keyword

nonn

Author

Leroy Quet, Jun 28 2008

Extensions

Extended by Ray Chandler, Jun 24 2009

Status

approved