A228519 Numbers n such that sigma(n) = sigma(n - phi(n)), where sigma(n) is the sum of divisors of n and phi(n) is the Euler totient function of n.

9356, 52412, 110442, 160834, 220884, 266866, 289230, 321668, 420790, 441768, 533732, 556818, 578460, 643336, 731530, 841580, 883536, 1067464, 1113636, 1156920, 1286672, 1446150, 1463060, 1683160, 1767072, 2103950, 2134928, 2227272, 2313840, 2545888, 2573344, 2892300

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..1000

Formula

sigma(9356- phi(9356)) = sigma(9356 - 4676) = 16380 = sigma(9356).

Maple

with(numtheory); P:=proc(q) local n; for n from 1 to q do
if sigma(n)=sigma(n-phi(n)) then print(n); fi; od; end: P(10^9);

Mathematica

Select[Range[10^6], DivisorSigma[1, #] == DivisorSigma[1, # - EulerPhi@ #] &] (* Michael De Vlieger, Jun 21 2016 *)

Crossrefs

Cf. A000010, A000203, A051953, A067880.

Sequence in context: A004954 A004974 A251824 * A292283 A265457 A330902

Adjacent sequences: A228516 A228517 A228518 * A228520 A228521 A228522

Keyword

nonn,easy

Author

Paolo P. Lava, Jun 21 2016

Status

approved