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A103402
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Palindromes p such that pi(p) is a palindromic prime.
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5
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3, 4, 5, 6, 11, 33, 555, 878, 5775, 6116, 919919, 58633685, 129707921, 16958285961, 867275572768
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| From a suggestion from Zak Seidov (zakseidov(AT)yahoo.com), Feb 02 2005.
a(16) > 32*10^12. [From Donovan Johnson (donovan.johnson(AT)yahoo.com), Dec 03 2009]
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MATHEMATICA
| NextPalindrome[n_] := Block[ {l = Floor[ Log[10, n] + 1], idn = IntegerDigits[n]}, If[ Union[ idn] == {9}, Return[n + 2], If[l < 2, Return[n + 1], If[ FromDigits[ Reverse[ Take[ idn, Ceiling[l/2]]]] FromDigits[ Take[ idn, -Ceiling[l/2]]], FromDigits[ Join[ Take[ idn, Ceiling[l/2]], Reverse[ Take[ idn, Floor[l/2]]] ]], idfhn = FromDigits[ Take[ idn, Ceiling[l/2]]] + 1; idp = FromDigits[ Join[ IntegerDigits[ idfhn], Drop[ Reverse[ IntegerDigits[ idfhn]], Mod[l, 2]]]] ]]]];
p = 0; a = {}; Do[p = NextPalindrome[p]; q = PrimePi[p]; If[PrimeQ[q], r = IntegerDigits[q]; If[Reverse[r] == r, Print[{p, q}]; AppendTo[a, p]]], {n, 10^6}]; a
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CROSSREFS
| Cf. A046941, A046942, A103357, A103358, A103403.
Sequence in context: A089912 A047425 A048989 * A154664 A191750 A034448
Adjacent sequences: A103399 A103400 A103401 * A103403 A103404 A103405
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KEYWORD
| base,nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 03 2005
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EXTENSIONS
| a(15) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Dec 03 2009
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