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Search: id:A095216
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| A095216 |
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Smallest prime divisor of n-th partial concatenation is prime(n). |
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+0
2
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| 2, 1, 5, 11, 27, 81, 153, 91, 71, 183, 27, 67, 147, 219, 347, 99
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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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.
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MAPLE
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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 (mathar(AT)strw.leidenuniv.nl), Aug 03 2007
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CROSSREFS
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Sequence in context: A110352 A107310 A049950 this_sequence A063635 A013014 A012905
Adjacent sequences: A095213 A095214 A095215 this_sequence A095217 A095218 A095219
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Jun 10 2004
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Aug 03 2007
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