1,1

Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.

a(n) = P_A046942(n).

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; Do[p = NextPalindrome[p]; While[ !PrimeQ[p], p = NextPalindrome[ p]]; q = IntegerDigits[ PrimePi[ p]]; If[Reverse[q] == q, Print[{p, FromDigits[q]}]], {n, 10^4}] (from Robert G. Wilson v Feb 03 2005)

Cf. A046942, A103357, A103358, A103402, A103403.

Sequence in context: A073903 A091689 A046482 this_sequence A116692 A114983 A118950

Adjacent sequences: A046938 A046939 A046940 this_sequence A046942 A046943 A046944

base,nonn

Carlos B. Rivera F. (crivera(AT)primepuzzles.net)

11853735811 from Giovanni Resta (g.resta(AT)iit.cnr.it), May 14 2003