cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A367950 Lexicographically earliest sequence of distinct positive integers such that the sum of the distinct prime factors (sopf) of a(n) + a(n + 1) is a perfect cube.

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%I A367950 #10 Dec 31 2023 00:21:52
%S A367950 1,14,31,44,91,92,43,2,13,32,103,80,55,20,25,50,85,98,37,8,7,38,97,86,
%T A367950 49,26,19,56,79,104,121,62,73,110,115,68,67,116,109,74,61,122,163,132,
%U A367950 3,12,33,42,93,90,45,30,15,60,75,108,27,18,57,78,105,120,63,72,111,24,21,54,81,102
%N A367950 Lexicographically earliest sequence of distinct positive integers such that the sum of the distinct prime factors (sopf) of a(n) + a(n + 1) is a perfect cube.
%H A367950 Éric Angelini, <a href="https://cinquantesignes.blogspot.com/2023/12/palindromes-with-distinct-prime-factors.html">Sums of distinct prime factors</a>, Personal blog, December 2023.
%e A367950 a(1) + a(2) =  1 + 14 =  15 whose sopf is  8, a perfect cube.
%e A367950 a(2) + a(3) = 14 + 31 =  45 whose sopf is  8, a perfect cube.
%e A367950 a(5) + a(6) = 91 + 92 = 183 whose sopf is 64, a perfect cube.
%t A367950 a[1]=1;a[n_]:=a[n]=(k=1;While[MemberQ[ar=Array[a,n-1],k]|| !IntegerQ[Total[First/@FactorInteger[k+a[n-1]]]^(1/3)],k++];k);Array[a,70]
%Y A367950 Cf. A008472, A164788.
%K A367950 nonn
%O A367950 1,2
%A A367950 _Giorgos Kalogeropoulos_ and _Eric Angelini_, Dec 05 2023