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%I #10 Jun 14 2024 04:14:11
%S 0,1,2,2,3,3,4,4,4,5,8,11,14,16,18,21,23,25,26,29,30,32,34,36,37,39,
%T 42,43,46,47,47,50,53,54,55,58,60,61,62,65,66,67,68,71,72,74,76,77,79,
%U 80,82,84,86,87,90,91,92,94,96,97,99,99,100,101,103,105,106,108,110,112
%N Number of primes up to n-th palindromic number.
%F a(n) = A000720(A002113(n)). - _Michel Marcus_, Jun 14 2024
%e a(11)=8 because there are 8 primes up to 11th palindromic number (i.e. 22).
%o (Python)
%o from sympy import primepi
%o def A076890(n):
%o if n == 1: return 0
%o y = 10*(x:=10**(len(str(n+1>>1))-1))
%o return primepi((c:=n+1-x)*x+int(str(c)[-2::-1]or 0) if n<x+y else (c:=n+1-y)*y+int(str(c)[-1::-1]or 0)) # _Chai Wah Wu_, Jun 14 2024
%Y Cf. A000720, A002113.
%K base,nonn
%O 1,3
%A _Shyam Sunder Gupta_, Nov 25 2002