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A095216 Smallest prime divisor of n-th partial concatenation is prime(n). 2
2, 1, 5, 11, 27, 81, 153, 91, 71, 183, 27, 67, 147, 219, 347, 99, 831, 109, 627, 329, 1053, 363, 603, 357, 349, 219, 981, 129, 737, 369, 61, 3447, 849, 237, 1281, 693, 719, 691, 851, 19, 2349, 2277, 627, 4163, 3889, 831, 1049, 3973, 1557, 1037, 2943, 1189, 1851 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..53.

EXAMPLE

Smallest prime divisor of 21511 which is a concatenation of first four terms 2,1,5 and 11 is prime(4) = 7, 21511= 7^2*439.

MAPLE

catL := proc(L) local resul, a ; resul := 0 ; for a in L do resul := resul*10^(max(1, ilog10(a)+1))+a ; od ; RETURN(resul) ; end: A020639 := proc(n) op(1, op(1, ifactors(n)[2])) ; end: A095216 := proc(nmax) local a, anext, n; a := [2] ; while nops(a) < nmax do anext := 0 ; n := nops(a)+1 ; while A020639(catL([op(a), anext])) <> ithprime(n) do anext := anext+1 ; od; a := [op(a), anext] ; od ; RETURN(a) ; end: A095216(15) ; # R. J. Mathar, Aug 03 2007

CROSSREFS

Sequence in context: A107310 A277279 A049950 * A174317 A144237 A268295

Adjacent sequences:  A095213 A095214 A095215 * A095217 A095218 A095219

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Jun 10 2004

EXTENSIONS

More terms from R. J. Mathar, Aug 03 2007

a(17)-a(53) from Donovan Johnson, May 13 2010

STATUS

approved

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Last modified February 23 08:00 EST 2019. Contains 320420 sequences. (Running on oeis4.)