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%I #17 Jul 01 2023 09:30:01
%S 31,631,10631,55453628211510631,786655453628211510631,
%T 10591786655453628211510631
%N Primes in right concatenation of triangular numbers.
%C No further terms up to 1000 triangular numbers. - _Harvey P. Dale_, Jul 23 2012
%C A078891(1201), with 6560 digits, is the next term. - _Michael S. Branicky_, Jul 01 2023
%D Shyam Sunder Gupta, Smarandache Sequence of Triangular Numbers, Smarandache Notions Journal, (to appear in Vol. 14, 2003).
%e a(2) = 631 because in A078891 631 is the second prime.
%e 10631 is a prime and the concatenation of 10, 6, 3, 1.
%t a = 1; Do[ a = ToExpression[ StringJoin[ ToString[n(n + 1)/2], ToString[a]]]; If[ PrimeQ[a], Print[a]], {n, 2, 250} ]
%t nn=50;With[{c=Accumulate[Range[nn]]},Select[Table[FromDigits[ Flatten[ IntegerDigits/@ Reverse[Take[c,n]]]],{n,nn}],PrimeQ]] (* _Harvey P. Dale_, Jul 23 2012 *)
%Y Primes in A078891.
%K base,hard,nonn,less
%O 1,1
%A _Amarnath Murthy_, Feb 23 2002
%E Edited by _Robert G. Wilson v_, Mar 01 2002
%E Entry revised Feb 15 2004
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