A352598 a(n) is the product of the squares of the nonzero digits of n.

1, 4, 9, 16, 25, 36, 49, 64, 81, 1, 1, 4, 9, 16, 25, 36, 49, 64, 81, 4, 4, 16, 36, 64, 100, 144, 196, 256, 324, 9, 9, 36, 81, 144, 225, 324, 441, 576, 729, 16, 16, 64, 144, 256, 400, 576, 784, 1024, 1296, 25, 25, 100, 225, 400, 625, 900, 1225, 1600, 2025, 36, 36, 144, 324

Offset: 1

Author

Michel Marcus, Mar 22 2022

Keywords

• nonn
• base

Comments

a(n) = 1 iff n is a term > 0 of A007088. - Bernard Schott, Mar 24 2022

Crossrefs

Cf. A007088, A051801, A352172.

Programs

Mathematica

a[n_] := (Times @@ Select[IntegerDigits[n], # > 1 &])^2; Array[a, 65] (* Amiram Eldar, Mar 22 2022 *)

PARI

a(n) = vecprod(apply(x->x^2, select(x->(x>1), digits(n))));

Python

from math import prod
def a(n): return prod(int(d)**2 for d in str(n) if d != '0')
print([a(n) for n in range(1, 64)]) # Michael S. Branicky, Mar 22 2022

Python

from math import prod
def A352598(n): return prod(map(lambda x:(0, 1, 4, 9, 16, 25, 36, 49, 64, 81)[int(x)],filter(lambda x:x>'1',str(n)))) # Chai Wah Wu, Sep 17 2024

Formula

a(n) = A051801(n)^2.

a(10*n) = a(n). - Bernard Schott, Mar 24 2022