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A068147
Primes in right concatenation of triangular numbers.
1
31, 631, 10631, 55453628211510631, 786655453628211510631, 10591786655453628211510631
OFFSET
1,1
COMMENTS
No further terms up to 1000 triangular numbers. - Harvey P. Dale, Jul 23 2012
A078891(1201), with 6560 digits, is the next term. - Michael S. Branicky, Jul 01 2023
REFERENCES
Shyam Sunder Gupta, Smarandache Sequence of Triangular Numbers, Smarandache Notions Journal, (to appear in Vol. 14, 2003).
EXAMPLE
a(2) = 631 because in A078891 631 is the second prime.
10631 is a prime and the concatenation of 10, 6, 3, 1.
MATHEMATICA
a = 1; Do[ a = ToExpression[ StringJoin[ ToString[n(n + 1)/2], ToString[a]]]; If[ PrimeQ[a], Print[a]], {n, 2, 250} ]
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 *)
CROSSREFS
Primes in A078891.
Sequence in context: A089758 A078891 A078914 * A025009 A028004 A025007
KEYWORD
base,hard,nonn,less
AUTHOR
Amarnath Murthy, Feb 23 2002
EXTENSIONS
Edited by Robert G. Wilson v, Mar 01 2002
Entry revised Feb 15 2004
STATUS
approved