cp's OEIS Frontend

A361492 Common difference corresponding to increasing arithmetic progression of at least n >= 2 primes whose first term is A284708(n); a(1) = 1.

%I A361492 #31 Mar 24 2023 17:13:41
%S A361492 1,1,2,6,30,30,210,210,210,17430,30030,60060,510510,3573570
%N A361492 Common difference corresponding to increasing arithmetic progression of at least n >= 2 primes whose first term is A284708(n); a(1) = 1.
%C A361492 a(22) = 4609098694200 (see Penguin reference).
%D A361492 David Wells, The Penguin Dictionary of Curious and Interesting Numbers, Revised Edition, Penguin Books, London, England, 1997, entry 11410337850553, page 191.
%e A361492 Common difference and corresponding n primes in arithmetic progression.
%e A361492 a(1) = 1: (2);
%e A361492 a(2) = 1: (2, 3);
%e A361492 a(3) = 2: (3, 5, 7);
%e A361492 a(4) = 6: (11, 17, 23, 29);
%e A361492 a(5) = 30: (37, 67, 97, 127, 157);
%e A361492 a(6) = 30: (107, 137, 167, 197, 227, 257);
%e A361492 a(7) = 210: (409, 619, 829, 1039, 1249, 1459, 1669);
%e A361492 a(8) = 210: (409, 619, 829, 1039, 1249, 1459, 1669, 1879);
%e A361492 a(9) = 210: (409, 619, 829, 1039, 1249, 1459, 1669, 1879, 2089);
%o A361492 (PARI) isokd(p, n, d) = for (i=1, n, if (!isprime(p+(i-1)*d), return(0))); 1;
%o A361492 isokp(p, n) = for (d=1, p-1, if (isokd(p, n, d), return(d)););
%o A361492 a(n) = my(p=2, d); while (!(d=isokp(p, n)), p=nextprime(p+1)); d; \\ _Michel Marcus_, Mar 16 2023
%Y A361492 Cf. A284708.
%K A361492 nonn,more
%O A361492 1,3
%A A361492 _Bernard Schott_, Mar 14 2023