A328817 Numbers k such that at least 7 of k, k+1, ..., k+9 are divisible by their least prime factor squared.

3475, 18271, 25524, 25623, 45616, 55772, 72471, 72472, 104419, 121667, 133223, 133224, 149220, 164975, 165568, 165571, 172916, 180167, 180168, 203979, 203980, 219123, 260424, 261472, 261475, 334516, 334519, 364216, 381267, 393320, 393323, 402723, 412524, 420467, 420468

Offset

1,1

Links

David A. Corneth, Table of n, a(n) for n = 1..10000 (first 600 terms from Harvey P. Dale)

Example

203980 is a member since 2^2 | 203980, 37^2 | 203981, 13^2 | 203983, 2^2 | 203984, 3^2 | 203985, 7^2 | 203987, and 2^2 | 203988.

Mathematica

Flatten[Position[Partition[Table[If[Divisible[n, FactorInteger[n][[1, 1]]^2], 1, 0], {n, 420000}], 10, 1], _?(Total[#]>6&)]] (* Harvey P. Dale, Jan 02 2021 *)

Prog

(PARI) upto(n) = {my(l, c, res); l = List([0, 0, 0, 1, 0, 0, 0, 1, 1, 0]); c = 3; res = List(); for(i = 11, n, f = factor(i)[, 2]; c -= l[1]; listpop(l, 1); if(f[1] >= 2, c++; listput(l, 1) , listput(l, 0) ); if(c >= 7, listput(res, i-9); ) ); res } \\ David A. Corneth, Jan 02 2021

Crossrefs

Cf. A283050.

Sequence in context: A253365 A109484 A232889 * A159215 A176380 A156773

Adjacent sequences: A328814 A328815 A328816 * A328818 A328819 A328820

Keyword

nonn

Author

Sean A. Irvine (on behalf of Donald S. McDonald), Nov 07 2019

Status

approved