A352090 - OEIS

A352090

Numbers k such that k and k+1 are both tribonacci-Niven numbers (A352089).

1, 6, 7, 12, 13, 20, 26, 27, 39, 68, 75, 80, 81, 87, 115, 128, 135, 149, 176, 184, 185, 195, 204, 215, 224, 230, 236, 243, 264, 278, 284, 291, 344, 364, 399, 447, 506, 507, 519, 548, 555, 560, 575, 595, 615, 635, 656, 664, 665, 684, 704, 725, 744, 777, 804, 824

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OFFSET

1,2

COMMENTS

Numbers k such that A278043(k) | k and A278043(k+1) | k+1.

The odd tribonacci numbers, A000073(A042964(m)), are all terms.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

EXAMPLE

6 is a term since 6 and 7 are both tribonacci-Niven numbers: the minimal tribonacci representation of 6, A278038(6) = 110, has 2 1's and 6 is divisible by 2, and the minimal tribonacci representation of 7, A278038(7) = 1000, has one 1 and 7 is divisible by 1.

MATHEMATICA

t[1] = 1; t[2] = 2; t[3] = 4; t[n_] := t[n] = t[n - 1] + t[n - 2] + t[n - 3]; q[n_] := Module[{s = {}, m = n, k}, While[m > 0, k = 1; While[t[k] <= m, k++]; k--; AppendTo[s, k]; m -= t[k]; k = 1]; Divisible[n, DigitCount[Total[2^(s - 1)], 2, 1]]]; Select[Range[1000], q[#] && q[# + 1] &]

CROSSREFS

Cf. A000073, A042964, A278038, A278043.

Subsequence of A352089.

Subsequences: A352091, A352092.

Similar sequences: A330927, A328205, A328209, A328213, A330931, A331086, A333427, A334309, A331820, A342427, A344342, A351715, A351720.

Sequence in context: A374810 A374920 A191337 * A276089 A037364 A315833

Adjacent sequences: A352087 A352088 A352089 * A352091 A352092 A352093

KEYWORD

nonn,base

AUTHOR

Amiram Eldar, Mar 04 2022

STATUS

approved