A051639 - OEIS

A051639

Concatenation of 3^k, k = 0,..,n.

1, 13, 139, 13927, 1392781, 1392781243, 1392781243729, 13927812437292187, 139278124372921876561, 13927812437292187656119683, 1392781243729218765611968359049, 1392781243729218765611968359049177147, 1392781243729218765611968359049177147531441

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OFFSET

0,2

REFERENCES

A. Murthy, Smarandache Notions Journal, Vol. 11 N. 1-2-3 Spring 2000

LINKS

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

EXAMPLE

139 belongs to the sequence because it is the concatenation of 3^0, 3^1 and 3^2.

MAPLE

From R. J. Mathar, Oct 10 2010: (Start)

cat2 := proc(a, b) dgsb := max(1, ilog10(b)+1) ; a*10^dgsb+b ; end proc:

catL := proc(L) local a; a := op(1, L) ; for i from 2 to nops(L) do a := cat2(a, op(i, L)) ; end do; a; end proc:

A051639 := proc(n) catL([seq(3^k, k=0..n)]) ; end proc: seq(A051639(n), n=0..20) ; (End)

# second Maple program:

a:= proc(n) a(n):= `if`(n<0, 0, parse(cat(a(n-1), 3^n))) end:

seq(a(n), n=0..12); # Alois P. Heinz, May 30 2021

MATHEMATICA

With[{p3=3^Range[0, 15]}, Table[FromDigits[Flatten[IntegerDigits/@ Take[ p3, n]]], {n, 15}]] (* Harvey P. Dale, Sep 13 2011 *)

CROSSREFS

Cf. A000244. - R. J. Mathar, Oct 10 2010

Sequence in context: A064103 A266630 A186506 * A138931 A157160 A263480

Adjacent sequences: A051636 A051637 A051638 * A051640 A051641 A051642

KEYWORD

base,nonn

AUTHOR

Felice Russo, Nov 15 1999

EXTENSIONS

Terms n>=7 corrected by R. J. Mathar, Oct 10 2010

STATUS

approved