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Search: id:A124232
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| A124232 |
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Numbers n such that prime(n) and pi(n) are palindromic. |
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| 1, 2, 3, 4, 5, 26, 32, 36, 138, 3691, 6987, 7193, 86969, 117766, 127150, 142583, 515786, 531448, 539596, 615980, 646060, 17262354, 39816443, 47548105, 48803361, 49426747, 528977302, 538348374, 1475057753, 1559827952, 2994135736
(list; graph; listen)
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OFFSET
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1,2
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MATHEMATICA
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NextPalindrome[n_] := Block[{lg = Floor@ Log[10, n] + 1, idn = IntegerDigits@n}, If[Union@ idn == {9}, Return[n + 2], If[lg < 2, Return[n + 1], If[ FromDigits@ Reverse@ Take[idn, Ceiling[lg/2]] > FromDigits@ Take[idn, -Ceiling[lg/2]], FromDigits@ Join[ Take[idn, Ceiling[lg/2]], Reverse@ Take[idn, Floor[lg/2]]], idfhn = FromDigits@ Take[idn, Ceiling[lg/2]] + 1; idp = FromDigits@ Join[IntegerDigits@ idfhn, Drop[ Reverse@ IntegerDigits@ idfhn, Mod[lg, 2]]] ]]]];
palQ[n_Integer] := Module[{idn = IntegerDigits@n}, idn == Reverse@ idn]; lst = {}; k = 1; While[k < 10^12, If[ PrimeQ@k && palQ@PrimePi@PrimePi@k, Print@PrimePi@k; AppendTo[lst, PrimePi@k]]; k = NextPalindrome@k]; lst (* Robert G. Wilson v *)
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CROSSREFS
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Subsequence of A075807 = numbers n such that n-th prime is palindromic.
Sequence in context: A080695 A088865 A075807 this_sequence A051143 A084853 A115337
Adjacent sequences: A124229 A124230 A124231 this_sequence A124233 A124234 A124235
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KEYWORD
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base,nonn
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AUTHOR
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Tanya Khovanova (tanyakh(AT)yahoo.com), Dec 13 2006
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EXTENSIONS
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a(22) - a(26) from Robert G. Wilson v (rgwv(at)rgwv.com), Dec 14 2006
a(27) - a(31) from Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 14 2006
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