A218072 Product of the nonzero digits (in base 10) of n^2.

1, 4, 9, 6, 10, 18, 36, 24, 8, 1, 2, 16, 54, 54, 20, 60, 144, 24, 18, 4, 16, 128, 90, 210, 60, 252, 126, 224, 32, 9, 54, 8, 72, 30, 20, 108, 162, 64, 10, 6, 48, 168, 288, 162, 20, 12, 36, 24, 8, 10, 12, 56, 144, 108, 30, 54, 216, 216, 96, 18, 42, 384, 1458

Offset: 1

Author

Nels Olson, Oct 19 2012

Keywords

• nonn
• base

Examples

			a(32) = 8 because 32*32 = 1024 and 1*2*4 = 8.
		

Crossrefs

Similar to A053667, which does not exclude zero digits from the product.

Related to A218013.

Cf. A000290, A051801.

Programs

Mathematica

Table[Times@@(IntegerDigits[n^2]/.(0->1)),{n,120}] (* Harvey P. Dale, Dec 12 2017 *)

PARI

a(n) = {digs = digits(n^2); prod(i=1, #digs, if (digs[i], digs[i], 1));} \\ Michel Marcus, Aug 12 2013

PARI

a(n) = vecprod(select(x->(x>1), digits(n^2))); \\ Michel Marcus, Mar 07 2022

Formula

a(n) = A051801(n^2). - Michel Marcus, Mar 07 2022