cp's OEIS Frontend

A175270 Numbers k such that the least number of squares that add up to k equals the least number of triangular numbers that add up to k. Equivalently, A002828(k) = A061336(k).

%I A175270 #12 Mar 17 2022 13:39:07
%S A175270 0,1,2,13,14,18,19,20,29,33,34,35,36,37,44,54,58,59,61,62,65,72,73,75,
%T A175270 77,86,90,96,97,101,106,107,118,129,130,131,134,137,138,140,146,147,
%U A175270 148,152,155,157,158,160,161,164,166,176,179,181,184,187,193,195,200
%N A175270 Numbers k such that the least number of squares that add up to k equals the least number of triangular numbers that add up to k. Equivalently, A002828(k) = A061336(k).
%H A175270 Charles R Greathouse IV, <a href="/A175270/b175270.txt">Table of n, a(n) for n = 1..10000</a>
%o A175270 (PARI) is2s(n)=my(f=factor(n>>valuation(n, 2))); for(i=1, #f~, if(bitand(f[i, 2], 1) && bitand(f[i, 1], 3)==3, return(0))); 1
%o A175270 is2t(n)=my(m9=n%9,f); if(m9==5 || m9==8, return(0)); is2s(4*n+1)
%o A175270 is(n)=my(o2=valuation(n, 2),f); if(n==0, return(1)); if(bitand(o2, 1)==0 && bitand(n>>o2, 7)==7, return(0)); if(issquare(n), return(ispolygonal(n,3))); if(ispolygonal(n,3), return(0)); is2t(n)==is2s(n) \\ _Charles R Greathouse IV_, Mar 17 2022
%Y A175270 Cf. A000217, A000290, A002828, A061336.
%K A175270 nonn,easy
%O A175270 1,3
%A A175270 _Ctibor O. Zizka_, Mar 19 2010
%E A175270 Data corrected and extended by _Mohammed Yaseen_, Mar 17 2022