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A068147 Primes in right concatenation of triangular numbers. 1

%I

%S 31,631,10631,55453628211510631,786655453628211510631,

%T 10591786655453628211510631

%N Primes in right concatenation of triangular numbers.

%C No further terms up to 1,000 triangular numbers. From _Harvey P. Dale_, Jul 23 2012

%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,more,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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Last modified August 15 09:02 EDT 2022. Contains 356135 sequences. (Running on oeis4.)