



0, 21, 22, 45, 46, 57, 70, 94, 105, 118, 142, 147, 165, 171, 177, 187, 190, 214, 221, 222, 225, 237, 238, 261, 267, 281, 286, 291, 313, 315, 318, 334, 345, 350, 357, 358, 381, 382, 387, 403, 430, 437, 441, 448, 465, 477, 478, 501, 507, 538, 555, 558, 561, 565
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OFFSET

1,2


COMMENTS

k is in this sequence if and only if the primes p less than or equal to (k+2)/(2+(k mod 2)) such that the sum of digits of k+1 in base p is at least p are also the primes less than or equal to (k+3)/(2+((k+1) mod 2)) such that the sum of digits of k+2 in base p is at least p.
For the comment above and the fact that the sequence is infinite, see Thm. 2 in "PowerSum Denominators" and Cor. 3 in "The denominators of power sums of arithmetic progressions".  Bernd C. Kellner and Jonathan Sondow, May 24 2017


LINKS



EXAMPLE

21 and 22 are in this sequence because {2, 3, 5} is the set of primes which meet the given constraints. Let sd(n, p) denote the sum of digits of n in base p, then we have:
2 <= sd(22, 2) = 3; 3 <= sd(22, 3) = 4; 5 <= sd(22, 5) = 6;
2 <= sd(23, 2) = 4; 3 <= sd(23, 3) = 5; 5 <= sd(23, 5) = 7;
2 <= sd(24, 2) = 2; 3 <= sd(24, 3) = 4; 5 <= sd(24, 5) = 8.
All other candidates do not satisfy the requirements: sd(22,7) = 4; sd(22,11) = 2; sd(23,7) = 5; sd(24,7) = 6; sd(24,11) = 4; sd(24,13) = 12.


MATHEMATICA

1 + SequencePosition[Table[Denominator[Together[(BernoulliB[n + 1, x]  BernoulliB[n + 1])]], {n, 0, 600}], w_ /; And[SameQ @@ w, Length@ w == 2]][[All, 1]] (* Michael De Vlieger, Sep 22 2017, after Jonathan Sondow at A195441 *)


PROG

(Julia)
L = fmpz[]; a = fmpz(0)
for n in 0:bound
a == u && push!(L, n1)
a = u
end
L end


CROSSREFS



KEYWORD

nonn,changed


AUTHOR



STATUS

approved



