A271266 a(n) = Product_{k=1..n} (k^2 + 21).

1, 22, 550, 16500, 610500, 28083000, 1600731000, 112051170000, 9524349450000, 971483643900000, 117549520911900000, 16692031969489800000, 2754185274965817000000, 523295202243505230000000, 113555058886840634910000000, 27934544486162796187860000000, 7737868822667094544037220000000

Offset

0,2

Comments

Yin et al. prove that a(n) is never a square for n > 0.

Links

Table of n, a(n) for n=0..16.

Q. Yin, Q. Tan and Y. Luo, p-Adic Valuation of (12+21)...(n2+21) and Applications, Southeast Asian Bulletin of Mathematics, Vol. 39(5) (2015) page: 747-754.

Mathematica

Table[Product[k^2 + 21, {k, n}], {n, 0, 16}] (* Michael De Vlieger, Apr 03 2016 *)

Prog

(PARI) a(n) = prod(k=1, n, (k^2+21));

Crossrefs

Cf. A101686, A241851.

Sequence in context: A182610 A320766 A203456 * A333899 A239652 A223883

Adjacent sequences: A271263 A271264 A271265 * A271267 A271268 A271269

Keyword

nonn

Author

Michel Marcus, Apr 03 2016

Status

approved