A357958 a(n) = 5*A005259(n) + 14*A005258(n-1).

39, 407, 7491, 167063, 4112539, 107461667, 2923006251, 81853622423, 2343591359499, 68288538877907, 2018394003648391, 60366962358086243, 1823569260750104179, 55557874330437332267, 1705172670555862322491, 52672612525369663916183

Offset

1,1

Comments

Conjectures:

1) a(p) == a(1) (mod p^5) for all primes p >= 5 (checked up to p = 271).

2) a(p^r) == a(p^(r-1)) ( mod p^(3*r+3) ) for r >= 2 and for all primes p >= 3.

These are stronger supercongruences than those satisfied separately by the two types of Apéry numbers A005258 and A005259. Cf. A357959.

There is also a product version of these conjectures:

3) the sequence {u(n): n>= 1} defined by u(n) = A005259(n)^25 * A005258(n-1)^14 conjecturally satisfies the congruences in 1) and 2) above.

Links

Table of n, a(n) for n=1..16.

Formula

a(n) = 5*Sum_{k = 0..n} binomial(n,k)^2*binomial(n+k,k)^2 + 14*Sum_{k = 0..n-1} binomial(n-1,k)^2*binomial(n+k-1,k).

a(p^r) == a(p^(r-1)) ( mod p^(3*r) ) for positive integer r and for all primes p >= 5.

Example

Examples of supercongruences:
a(13) - a(1) = 1823569260750104179 - 39 = (2^2)*5*7*(13^5)*35081444357 == 0 (mod 13^5).
a(7^2) - a(7) = (2^3)*(7^9)* 10412078726049425470554760052126170543547100055154203726400782433 == 0 (mod 7^9).

Maple

seq( add( 5*binomial(n, k)^2*binomial(n+k, k)^2 + 14*binomial(n-1, k)^2* binomial(n+k-1, k), k = 0..n ), n = 1..20);

Crossrefs

Cf. A005258, A005259, A212334, A352655, A357567, A357956, A357957, A357959, A357960.

Sequence in context: A210335 A210328 A231993 * A229517 A254871 A193072

Adjacent sequences: A357955 A357956 A357957 * A357959 A357960 A357961

Keyword

nonn,easy

Author

Peter Bala, Oct 25 2022

Status

approved