A370671 a(n) = Sum_{i=2..n-1} i*n^(i-2).

0, 0, 0, 2, 14, 117, 1244, 16340, 256794, 4708235, 98765432, 2334368214, 61405650470, 1779714835745, 56358445438164, 1936265501684072, 71737338064426034, 2851241711464855575, 121019325106640638448, 5463472083532379956970, 261417839335180055401662, 13215375398730198560266829

Offset

0,4

Comments

Digits 2..(n-1) in strict descending order (n-1)..2 interpreted in base n.

Upper bound of A370371(n) when n is odd and n-1 has an even 2-adic valuation.

Links

Table of n, a(n) for n=0..21.

Formula

a(n) = (n - 2)*(n^(n - 1) - 1)/(n - 1)^2 for n > 1.

Prog

(Python)
def A370671(n): return (n-2)*(n**(n-1)-1)//(n-1)**2 if n > 1 else 0

Crossrefs

Cf. A062813, A051846, A370371.

Sequence in context: A231615 A277467 A208393 * A361962 A192457 A351856

Adjacent sequences: A370668 A370669 A370670 * A370672 A370673 A370674

Keyword

nonn

Author

Chai Wah Wu, Feb 25 2024

Status

approved