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
Keywords
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)
Programs
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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
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