A105988 Near-repdigit semiprimes with 7 as repeated digit.

177, 377, 707, 717, 737, 767, 771, 778, 779, 3777, 4777, 5777, 7277, 7377, 7737, 7747, 7771, 7773, 7778, 7779, 7787, 7977, 8777, 9777, 17777, 37777, 57777, 70777, 77177, 77277, 77677, 77757, 77767, 77771, 277777, 577777, 677777, 707777, 737777

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

a(2)=377 is a term because 377 is a semiprime and all digits are equal to 7 except one.

Mathematica

Rest[Flatten[Table[Select[FromDigits/@Flatten[Permutations/@Table[ PadRight[ {n}, k, 7], {n, 0, 9}], 1], PrimeOmega[#]==2&], {k, 3, 7}]]]//Union (* Harvey P. Dale, Jul 25 2020 *)

Crossrefs

Sequence in context: A169641 A255786 A147028 * A292185 A083620 A097317

Adjacent sequences: A105985 A105986 A105987 * A105989 A105990 A105991

Keyword

base,nonn

Author

Shyam Sunder Gupta, Apr 29 2005

Status

approved