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A068147 Primes in right concatenation of triangular numbers. 1
31, 631, 10631, 55453628211510631, 786655453628211510631, 10591786655453628211510631 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

No further terms up to 1,000 triangular numbers.  From Harvey P. Dale, Jul 23 2012

REFERENCES

Shyam Sunder Gupta, Smarandache Sequence of Triangular Numbers, Smarandache Notions Journal, (to appear in Vol. 14, 2003).

LINKS

Table of n, a(n) for n=1..6.

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

Adjacent sequences:  A068144 A068145 A068146 * A068148 A068149 A068150

KEYWORD

base,hard,more,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

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Last modified August 25 03:10 EDT 2019. Contains 326318 sequences. (Running on oeis4.)