A124179 - OEIS

A124179

a(n) = prime(R(prime(n))) where prime(i) is the i-th prime and R(p) is the value of the reverse of the digits of p.

3, 5, 11, 17, 31, 127, 353, 467, 131, 479, 41, 367, 43, 139, 373, 149, 499, 53, 383, 59, 157, 509, 163, 521, 401, 547, 1993, 5281, 7001, 2063, 5449, 739, 5527, 7307, 7417, 877, 5701, 2437, 5801, 2539, 7649, 1087, 1153, 2689, 6067, 7841, 613, 2137, 5471

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Paolo Xausa, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A000040(A004086(A000040(n))) = A000040(A004087(n)). - Paolo Xausa, Dec 22 2025

EXAMPLE

For n = 7, prime(7) = 17, R(17) = 71, and prime(71) = 353. [Edited by Paolo Xausa, Dec 22 2025]

MAPLE

R:= n-> (s-> parse(cat(s[-i]$i=1..length(s))))(""||n):

a:= n-> ithprime(R(ithprime(n))):