A290572 Least number that is the start of a gap of size n between numbers that are either prime or twice a prime (A001751).

2, 11, 7, 67, 53, 47, 514, 401, 317, 181, 467, 526, 1069, 2819, 1262, 3142, 1382, 1913, 1327, 4178, 2477, 9697, 8123, 8329, 3274, 11213, 21031, 5119, 16382, 13063, 20446, 44417, 22193, 37747, 12854, 46957, 35617, 63863, 48679, 20809, 76166, 39251, 110359, 59282, 136898, 212923, 143006

Offset

1,1

Comments

Numbers that are less than any later number are recorded in A290488.

Links

Robert G. Wilson v, Table of n, a(n) for n = 1..261

Robert G. Wilson v, Table of n, a(n) for n = 0..290, or 0 if no such value is known.

Example

a(1) is  2 since  3 -  2 = 1;
a(2) is 11 since 13 - 11 = 2;
a(3) is  7 since 10 -  7 = 3;
a(4) is 67 since 71 - 67 = 4; etc.

Mathematica

nxt[n_] := Block[{k = n +1}, While[ !PrimeQ[k] && !PrimeQ[k/2], k++]; k]; p = 2; q = 3; t[_] = 0; While[p < 215000, d = q - p; If[ t[d] == 0, t[d] = p]; p = q; q = nxt@ q]; t@# & /@ Range@ 47

Crossrefs

Cf. A001751, A002386, A290488, A290489.

Sequence in context: A224210 A344776 A368640 * A220771 A375881 A277055

Adjacent sequences: A290569 A290570 A290571 * A290573 A290574 A290575

Keyword

nonn

Author

Bobby Jacobs and Robert G. Wilson v, Aug 06 2017

Status

approved