A321023 Numbers k such that sigma(k) = sigma(k + 15).

26, 62, 20840574, 25741470, 60765690, 102435795, 277471467, 361466454, 464465910, 1110512403, 1927430490, 2741174163, 3631266639, 3844534602, 3982743750, 4565968407, 4612184562, 4829319495, 4981969978, 7066794735, 13484870399, 14268004443, 14550390855, 15051147111

Offset: 1

Author

Tomohiro Yamada, Oct 26 2018

Keywords

• nonn

Examples

			sigma(26) = sigma(41) = 42, sigma(62) = sigma(77) = 96.
		

Links

• Giovanni Resta, Table of n, a(n) for n = 1..116 (terms < 2.5*10^12)

Crossrefs

Cf. A002961, A007373, A015861, A015863, A015865, A015866, A015867, A015876, A015877, A015880, A015881, A015882, A015883, A172335, A181647, A172333.

Programs

PARI

my(V=vector(15)); for(n=1, 2^28, my(s=sigma(n), r=(n%15)+1); if (s==V[r], print1(n-15, ", ")); V[r]=s)

Extensions

a(7)-a(9) from Amiram Eldar, Oct 26 2018

a(10)-a(24) from Giovanni Resta, Oct 26 2018