A377736 - OEIS

%I #7 Nov 06 2024 04:40:06

%S 154,282674,3003599678

%N Numbers k such that k, k+1 and k+2 are all terms in A377732.

%D 144544673718847655 and 10931129469745989328319 are also terms (De Koninck et al., 2024, section 6).

%H Jean-Marie De Koninck, A. Arthur Bonkli Razafindrasoanaivolala, and Hans Schmidt Ramiliarimanana, <a href="https://doi.org/10.1007/s40993-024-00520-x">Integers with a sum of co-divisors yielding a square</a>, Research in Number Theory, Vol. 10, No. 2 (2024), Article 30; <a href="https://www.jeanmariedekoninck.mat.ulaval.ca/fileadmin/Documents/Publications/2023_integers_with_a_sum_of_co-divisors_yielding_a_square.pdf">author's copy</a>.

%o (PARI) is1(k) = if(issquare(k), issquare(2 * sqrtint(k)), my(d = divisors(k), nh = #d/2); issquare(d[nh] + d[nh + 1]));

%o lista(kmax) = {my(q1 = is1(1), q2 = is1(2), q3); for(k = 3, kmax, q3 = is1(k); if(q1 && q2 && q3, print1(k-2, ", ")); q1 = q2; q2 = q3);}

%Y Subsequence of A377732 and A377733.

%K nonn,more,bref

%O 1,1

%A _Amiram Eldar_, Nov 05 2024