%I #8 Jan 16 2023 21:41:08
%S 1,4,148,5821348,13748537282247342677718148,
%T 49900608324196518198677680899235165296598423281799348
%N Numbers k such that triangular(k)-1 is a square and triangular(k)+1 is a prime number.
%C a(7) has 191 decimal digits: 314305920...194453348.
%C Corresponding primes and roots of squares: A226072 and A226074.
%Y Cf. A226069-A226074.
%K nonn
%O 1,2
%A _Alex Ratushnyak_, May 25 2013