A141266 Concatenate double factorials.

1, 12, 123, 1238, 123815, 12381548, 12381548105, 12381548105384, 12381548105384945, 123815481053849453840, 12381548105384945384010395, 1238154810538494538401039546080, 1238154810538494538401039546080135135

Offset

0,2

Links

Table of n, a(n) for n=0..12.

Florentin Smarandache Smarandache Concatenated Sequences

Formula

a(n) = a(n-1)*10^floor(1+log_10(n!!)) + n!!, with a(1)=1.

Maple

P:=proc(i) local a, j, k, n; a:=1; print(1); for n from 2 by 1 to i do k:=n; j:=n-2; while j>0 do k:=k*j; j:=j-2; od; a:=a*10^floor(evalf(1+log10(k), 1000))+k; print(a); od; end: P(20);

Crossrefs

Cf. A045508, A141265, A141267.

Sequence in context: A159901 A159900 A134802 * A083429 A226737 A077306

Adjacent sequences: A141263 A141264 A141265 * A141267 A141268 A141269

Keyword

nonn,base

Author

Paolo P. Lava, Jun 20 2008

Status

approved