A186698 Next prime after n-th positive palindrome.
2, 3, 5, 5, 7, 7, 11, 11, 11, 13, 23, 37, 47, 59, 67, 79, 89, 101, 103, 113, 127, 137, 149, 157, 163, 173, 191, 193, 211, 223, 223, 233, 251, 257, 263, 277, 283, 293, 307, 317, 331, 337, 347, 359, 367, 379, 389, 397, 409, 419, 431, 439, 449, 457, 467, 479, 487, 499, 509, 521, 541, 541, 547, 557, 569, 577, 587, 599, 607, 617, 631, 641, 647
Offset: 1
Links
- Chai Wah Wu, Table of n, a(n) for n = 1..10000
Programs
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Maple
digrev:= proc(x) option remember; local t; t:= x mod 10; t*10^ilog10(x)+procname((x-t)/10) end proc: for x from 0 to 9 do digrev(x):= x od: N:=6; Pals:= $1..9: for d from 2 to N do if d::even then m:= d/2; Pals:= Pals, seq(n*10^m + digrev(n), n=10^(m-1)..10^m-1); else m:= (d-1)/2; Pals:= Pals, seq(seq(n*10^(m+1)+y*10^m+digrev(n), y=0..9), n=10^(m-1)..10^m-1); fi od: Pals:=[Pals]: map(nextprime,Pals); # Robert Israel, Nov 04 2015 -
Mathematica
NextPrime[Select[Range[700],PalindromeQ]] (* Harvey P. Dale, Jan 31 2024 *)
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Python
from sympy import nextprime def A186698(n): return int(nextprime((c:=n+1-x)*x+int(str(c)[-2::-1] or 0) if n+1<(x:=10**(len(str(n+1>>1))-1))+(y:=10*x) else (c:=n+1-y)*y+int(str(c)[::-1] or 0))) # Chai Wah Wu, Jul 10 2024
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