A106474 - OEIS

A106474

a(n) = A006579(4n+4)/4.

1, 3, 7, 8, 13, 19, 19, 20, 33, 35, 31, 48, 37, 51, 75, 48, 49, 87, 55, 88, 109, 83, 67, 116, 105, 99, 135, 128, 85, 195, 91, 112, 177, 131, 199, 216, 109, 147, 211, 212, 121, 283, 127, 208, 333, 179, 139, 272, 217, 275, 279, 248, 157, 351, 323, 308, 313, 227, 175

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OFFSET

0,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 0..10000

FORMULA

a(n) = Sum_{k=0..4n+2} gcd(4n-k+3, k+1)/4.

MATHEMATICA

Table[Sum[GCD[4n-k+3, k+1]/4, {k, 0, 4n+2}], {n, 0, 60}] (* Harvey P. Dale, May 19 2019 *)

f[p_, e_] := (e*(p - 1)/p + 1)*p^e; a[n_] := (Times @@ f @@@ FactorInteger[4*n+4]) / 4 - n - 1; Array[a, 100, 0] (* Amiram Eldar, Apr 26 2023 *)

CROSSREFS

Cf. A006579.