A078263 Product of the forward and reverse concatenations of 1 to n.

1, 252, 39483, 5332114, 670592745, 80779853376, 9449772114007, 1082152022374638, 121932631112635269, 135650052221140070110, 1371589685334334871208531, 14951973660666886818972704952, 161989023197512459256340110001373, 1744593949735321085709329564827297794

Offset: 1

Author

Amarnath Murthy, Nov 24 2002

Keywords

• base
• nonn

Examples

			a(3) = 123*321 = 39483.
		

Crossrefs

Cf. A000422, A007908, A078264.

Programs

Maple

a:= n-> parse(cat(1+n-i$i=1..n))*parse(cat($1..n)):
seq(a(n), n=1..14);  # Alois P. Heinz, Jun 25 2025

Mathematica

frc[n_]:=Module[{r1=FromDigits[Flatten[IntegerDigits/@Range[n]]], r2 = FromDigits[ Flatten[ IntegerDigits/@Range[n,1,-1]]]},r1*r2]; Array[ frc, 20] (* Harvey P. Dale, Aug 24 2015 *)

Formula

a(n) = A000422(n) * A007908(n). - Sean A. Irvine, Jun 25 2025

Extensions

More terms from Sascha Kurz, Jan 04 2003

More terms from Sean A. Irvine, Jun 25 2025