cp's OEIS Frontend

A173015 Numbers k such that sequence of type a_k(n): {a(1) = 1, for n >= 2: a(n) = the smallest number h such that sigma(h) = A000203(h) = a(n-1) + k, a(n) = 0 if no such number exists} is sequence A063524(n) for n >= 1.

%I A173015 #10 Mar 22 2024 06:48:59
%S A173015 9,10,16,21,22,25,26,33,34,45,46,49,50,51,52,58,64,65,66,69,70,75,76,
%T A173015 81,82,85,86,87,88,94,99,100,105,106,115,116,117,118,122,129,130,134,
%U A173015 135,136,141,142,145,146,147,148,153,154,165,166,169,172,177,178,184,187,188,189,190,196
%N A173015 Numbers k such that sequence of type a_k(n): {a(1) = 1, for n >= 2: a(n) = the smallest number h such that sigma(h) = A000203(h) = a(n-1) + k, a(n) = 0 if no such number exists} is sequence A063524(n) for n >= 1.
%C A173015 Sequence of composite numbers.
%C A173015 A063524(n) = characteristic function of 1 = 1,0,0,0,0,0,0,0,0,0,0,0, ...
%C A173015 Numbers k such that A051444(k) = A051444(k+1) = 0.
%C A173015 Complement of A173016.
%H A173015 Amiram Eldar, <a href="/A173015/b173015.txt">Table of n, a(n) for n = 1..10000</a>
%e A173015 a(1) = k = 9 because a_9(n) = A063524(n) = 1,0,0,0,0,0,0,0,0,0,0,0, ...
%t A173015 seq[max_] := Module[{t = Table[1, {max}]}, t[[Complement[Range[max], Table[ DivisorSigma[1, n], {n, 1, max}]]]] = 0; SequencePosition[t, {0, 0}][[;; , 1]]]; seq[200] (* _Amiram Eldar_, Mar 22 2024 *)
%Y A173015 Cf. A000035, A000203, A051444, A063524, A173012, A173013, A173014, A173016.
%K A173015 nonn
%O A173015 1,1
%A A173015 _Jaroslav Krizek_, Nov 06 2010
%E A173015 More terms from _Amiram Eldar_, Mar 22 2024