A380011 Beginning with 7, least prime such that the reversal concatenation of the first n terms is prime.
7, 3, 3, 13, 3, 2, 13, 47, 43, 47, 37, 41, 109, 41, 139, 149, 109, 263, 73, 563, 163, 41, 19, 797, 61, 107, 31, 821, 43, 149, 37, 953, 211, 89, 547, 353, 337, 167, 67, 239, 1009, 449, 97, 23, 349, 41, 31, 911, 61, 929, 229, 797, 331, 191, 463, 107, 463, 809, 2887, 971
Offset: 1
Links
- J.W.L. (Jan) Eerland, Table of n, a(n) for n = 1..982
Programs
-
Mathematica
w={7};Do[k=1;q=Monitor[Parallelize[While[True,If[PrimeQ[FromDigits[Join@@IntegerDigits/@Reverse[IntegerDigits[FromDigits[Join@@IntegerDigits/@Append[w,Prime[k]]]]]]],Break[]];k++];Prime[k]],k];w=Append[w,q],{i,2,50}];w -
Python
from itertools import count, islice from gmpy2 import digits, is_prime, mpz, next_prime def agen(): # generator of terms r, an = "", 7 while True: yield int(an) r = digits(an)[::-1] + r p = 2 while not is_prime(mpz(digits(p)[::-1]+r)): p = next_prime(p) an = p print(list(islice(agen(), 50))) # after Michael S. Branicky in A379355
Comments