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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 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.)