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A357560 a(n) = the numerator of ( Sum_{k = 1..n} (-1)^(n+k)*(1/k)*binomial(n,k)* binomial(n+k,k)^2 ). 3
0, 4, 0, 94, 500, 19262, 50421, 2929583, 25197642, 2007045752, 3634262225, 368738402141, 6908530637021, 852421484283739, 1168833981781025, 56641833705924527, 276827636652242789, 46345946530867053437, 51051733540797155872, 9673584199611903429172 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
Define S_m(n) = the numerator of Sum_{k = 1..n} (-1)^(n+k)*(1/k^m)*binomial(n,k)* binomial(n+k,k)^2, so that S_0(n) = -1 + A005258(n), one of the two types of Apéry numbers. The present sequence is the case m = 1. See A357561 for the case m = 3.
Conjectures:
1) for even m >= 2, S_m(p-1) == 0 (mod p^3) for all primes p > m + 3.
2) for odd m >= 1, S_m(p-1) == 0 (mod p^4) for all primes p > m + 4.
LINKS
FORMULA
Conjecture: a(p-1) == 0 (mod p^4) for all primes p >= 7 (checked up to p = 499).
Note: the Apéry numbers B(n) = A005258(n) = Sum_{k = 0..n} (-1)^(n+k)* binomial(n,k)*binomial(n+k,k)^2 satisfy the supercongruences B(p-1) == 1 (mod p^3) for all primes p >= 5 (see, for example, Straub, Example 3.4).
EXAMPLE
Example of a supercongruence:
p = 19: a(19 - 1) = 51051733540797155872 = (2^5)*(19^4)*12241823444801 == 0 (mod 19^4).
MAPLE
seq( numer(add( (-1)^(n+k) * (1/k) * binomial(n, k) * binomial(n+k, k)^2, k = 1..n )), n = 0..20 );
CROSSREFS
Sequence in context: A298616 A366828 A337112 * A013037 A129814 A129825
KEYWORD
nonn,easy
AUTHOR
Peter Bala, Oct 04 2022
STATUS
approved

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Last modified February 24 22:04 EST 2024. Contains 370307 sequences. (Running on oeis4.)