A378978 - OEIS

A378978

Deficiency of even numbers: a(n) = 4*n - sigma(2*n).

1, 1, 0, 1, 2, -4, 4, 1, -3, -2, 8, -12, 10, 0, -12, 1, 14, -19, 16, -10, -12, 4, 20, -28, 7, 6, -12, -8, 26, -48, 28, 1, -12, 10, -4, -51, 34, 12, -12, -26, 38, -56, 40, -4, -54, 16, 44, -60, 25, -17, -12, -2, 50, -64, 4, -24, -12, 22, 56, -120, 58, 24, -60, 1, 8, -72, 64, 2, -12, -56, 68, -115, 70, 30, -72, 4, 20

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OFFSET

1,5

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..32769

Index entries for sequences related to sigma(n).

FORMULA

a(n) = A033879(2*n) = 4*n - A062731(n).

MATHEMATICA

a[n_]:= 4*n - DivisorSigma[1, 2*n]; Array[a, 77] (* Stefano Spezia, Dec 13 2024 *)

PROG

(PARI)