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A335774

Numbers k such that in prime factorization of k the second smallest factor is 7.

14, 21, 28, 35, 56, 63, 98, 112, 147, 154, 175, 182, 189, 196, 224, 231, 238, 245, 266, 273, 308, 322, 357, 364, 385, 392, 399, 406, 434, 441, 448, 455, 476, 483, 518, 532, 567, 574, 595, 602, 609, 616, 644, 651, 658, 665, 686, 693, 728, 742, 777, 784, 805, 812, 819, 826, 854, 861

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OFFSET

1,1

COMMENTS

Trivially, all terms are multiples of 7. Also terms are divisible by 2 or 3 or 5, and by any number of primes > 7.

LINKS

Ray Chandler, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, -1).

EXAMPLE

14 = 2*7, 28 = 2*2*7, 35 = 5*7, 56 = 2^3*7, 63 = 3*3*7, 147 = 3*7*7, 154 = 2*7*11.

MATHEMATICA

Select[Range[14, 1000], 1 < Length[fi = FactorInteger[#]] && 7 == fi[[2, 1]] &]