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A141266 Concatenate double factorials. 2
1, 12, 123, 1238, 123815, 12381548, 12381548105, 12381548105384, 12381548105384945, 123815481053849453840, 12381548105384945384010395, 1238154810538494538401039546080, 1238154810538494538401039546080135135 (list; graph; refs; listen; history; text; internal format)
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

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Last modified May 17 19:26 EDT 2021. Contains 343988 sequences. (Running on oeis4.)