A331759 a(n) = A115004(2n+1).

1, 31, 179, 585, 1463, 3065, 5729, 9797, 15737, 24087, 35315, 50073, 69025, 92871, 122475, 158681, 202529, 254597, 315957, 387977, 471589, 568227, 678971, 805241, 948515, 1109675, 1290839, 1493127, 1717571, 1966997, 2242925, 2547277, 2881033, 3246087, 3645459

Offset

0,2

Links

Chai Wah Wu, Table of n, a(n) for n = 0..10000

N. J. A. Sloane, Families of Essentially Identical Sequences, Mar 24 2021 (Includes this sequence)

Formula

a(n) = (2*n+1)^2 + Sum_{i=2..2n+1} (2*n+2-i)*(4*n+4-i)*phi(i). - Chai Wah Wu, Aug 17 2021

Prog

(Python)
from sympy import totient
def A331759(n): return (2*n+1)**2 + sum(totient(i)*(2*n+2-i)*(4*n+4-i) for i in range(2, 2*n+2)) # Chai Wah Wu, Aug 17 2021

Crossrefs

Cf. A115004, A331760.

Sequence in context: A296959 A140587 A142140 * A325080 A139496 A145838

Adjacent sequences: A331756 A331757 A331758 * A331760 A331761 A331762

Keyword

nonn

Author

N. J. A. Sloane, Feb 04 2020

Status

approved