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A141267 Concatenate first n double factorials in reverse order. 2
1, 21, 321, 8321, 158321, 48158321, 10548158321, 38410548158321, 94538410548158321, 384094538410548158321, 10395384094538410548158321, 4608010395384094538410548158321, 1351354608010395384094538410548158321 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

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

FORMULA

a(n)=n!!*10^floor{1+log10[a(n-1)]}+a(n-1), 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:=k*10^floor(evalf(1+log10(a), 1000))+a; print(a); od; end: P(20);

MATHEMATICA

FromDigits/@(Flatten[IntegerDigits/@Reverse[#]]&/@Table[ Take[Range[20]!!, n], {n, 20}]) (* Harvey P. Dale, Sep 30 2011 *)

CROSSREFS

Cf. A045508, A141265, A141266.

Sequence in context: A060554 A057610 A036737 * A016262 A001233 A145148

Adjacent sequences:  A141264 A141265 A141266 * A141268 A141269 A141270

KEYWORD

nonn,base

AUTHOR

Paolo P. Lava, Jun 20 2008

STATUS

approved

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Last modified October 21 08:47 EDT 2019. Contains 328292 sequences. (Running on oeis4.)