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 A260802 Odd numbers x = 2n - 1 such that the concatenation of A019519(n) and A038395(n-1) is prime. 0
 3, 13, 19, 21, 67 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE a(1) = 3 since 13_1 is prime; a(2) = 13 since 135791113_1197531 is prime; a(3) = 19 since 135791113151719_1715131197531 is prime. PROG (Python) import sympy n=1 while n>0: ....s=str(n) ....for m in range(n-2, 0, -2): ........s=str(m)+s+str(m) ....p=int(s) ....if sympy.isprime(p)==True: ........print(n) ....n=n+2 CROSSREFS Cf. A019519, A038395. Sequence in context: A024474 A024599 A071600 * A045435 A038974 A168425 Adjacent sequences:  A260799 A260800 A260801 * A260803 A260804 A260805 KEYWORD nonn,more,base AUTHOR Abhiram R Devesh, Jul 31 2015 STATUS approved

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Last modified September 23 22:32 EDT 2020. Contains 337315 sequences. (Running on oeis4.)