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 A179295 a(n) is the least prime number such that prime(n)+a(n)+1 is a prime or -1 if no such prime number exists. 1
 2, 3, 5, 3, 5, 3, 5, 3, 5, 7, 5, 3, 5, 3, 5, 5, 7, 5, 3, 7, 5, 3, 5, 7, 3, 5, 3, 5, 3, 13, 3, 5, 11, 11, 7, 5, 5, 3, 5, 5, 11, 11, 5, 3, 13, 11, 11, 3, 5, 3, 5, 11, 29, 5, 5, 5, 7, 5, 3, 11, 23, 13, 3, 5, 3, 13, 5, 11, 5, 3, 5, 7, 5, 5, 3, 5, 7, 3, 7, 11, 11 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS If Maillet's conjecture is true, then a(n) != -1 for all n. - Chai Wah Wu, Aug 01 2017 LINKS Chai Wah Wu, Table of n, a(n) for n = 1..10000 Wen Huang and XiaoSheng Wu, On the set of the difference of primes, Proc. Amer. Math. Soc. 145 (2017), 3787-3793. E. Maillet, Réponse, L’intermédiaire des math. 12 (1905), p. 108. EXAMPLE a(1) = 2, since prime(1) + 2 + 1 = 5. MATHEMATICA Table[Block[{p=2}, While[!PrimeQ[Prime[n] + p + 1], p=NextPrime[p]]; p], {n, 100}] (* Indranil Ghosh, Jun 30 2017 *) PROG (ANS Forth) \ https://github.com/Lehs/ANS-Forth-libraries s" numbertheory.4th" included : get_number \ p -- q locals| p | 1 begin nextprime dup p + 1+ isprime until ; : list_numbers \ N -- locals| N | 1 begin nextprime dup get_number cr . dup N > until ; (PARI) a(n) = my(pn=prime(n), p=2); while(! isprime(pn+p+1), p = nextprime(p+1)); p; \\ Michel Marcus, Jun 30 2017 (Python) from sympy import prime, isprime, nextprime def a(n): p=2 while not isprime(prime(n) + p + 1): p=nextprime(p) return p print([a(n) for n in range(1, 101)]) # Indranil Ghosh, Jun 30 2017 CROSSREFS Sequence in context: A201769 A077276 A073684 * A083776 A122820 A261324 Adjacent sequences: A179292 A179293 A179294 * A179296 A179297 A179298 KEYWORD nonn AUTHOR Lars-Erik Svahn, Jun 21 2017 EXTENSIONS Definition clarified by Chai Wah Wu, Aug 01 2017 More terms from Chai Wah Wu, Aug 02 2017 STATUS approved

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Last modified April 23 10:29 EDT 2024. Contains 371905 sequences. (Running on oeis4.)