A298729 Prime numbers whose decimal expansion includes a substring of seven consecutive 7's.

137777777, 177777773, 177777779, 197777777, 307777777, 347777777, 437777777, 527777777, 547777777, 577777777, 587777777, 647777777, 697777777, 777777701, 777777739, 777777743, 777777751, 777777799, 787777777, 827777777, 947777777, 967777777, 1247777777, 1277777771, 1277777773, 1457777777, 1487777777

Offset

1,1

Links

Table of n, a(n) for n=1..27.

Mathematica

s = {7, 7, 7, 7, 7, 7, 7}; lst = {}; k = 1; While[k < 10001, l = 1; il = 12;
While[l < il, p = FromDigits@ Flatten@ Insert[ IntegerDigits[k, 10, 10], s, l];
  If[PrimeQ@ p, AppendTo[lst, p]]; l++]; k++]; Union@ lst (* Robert G. Wilson v, Feb 08 2018 *)

Prog

(PARI) is(n) = my(v=vector(7, x, 7), d=digits(n)); for(k=1, #d-6, if([d[k], d[k+1], d[k+2], d[k+3], d[k+4], d[k+5], d[k+6]]==v, return(1))); 0
forprime(p=1, , if(is(p), print1(p, ", "))) \\ Felix Fröhlich, Mar 06 2018

Crossrefs

Cf. A102764, A167282, A108844, A083978.

Sequence in context: A034590 A185888 A105297 * A203505 A342214 A251505

Adjacent sequences: A298726 A298727 A298728 * A298730 A298731 A298732

Keyword

base,nonn,less

Author

Yohei Furutono, Jan 25 2018

Status

approved