

A085415


Take prime[n] and continue adding 1, 2, ..., a(n) until one reaches a prime.


7



1, 4, 3, 3, 3, 3, 3, 4, 3, 12, 3, 3, 3, 4, 3, 3, 12, 3, 3, 8, 3, 4, 3, 12, 3, 3, 3, 3, 7, 8, 4, 3, 8, 4, 12, 3, 3, 4, 3, 3, 12, 4, 3, 3, 8, 7, 7, 3, 3, 4, 3, 12, 4, 3, 3, 3, 12, 3, 3, 8, 4, 11, 3, 3, 8, 8, 3, 4, 3, 4, 3, 15, 3, 3, 4, 3, 12, 8, 11, 4, 24, 4, 8, 3, 4, 3, 15, 3, 3, 7, 8, 12, 8, 11, 4, 3, 12, 8
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OFFSET

1,2


COMMENTS

Prime[n] plus a triangular number is prime.  Harvey P. Dale, Jun 12 2013


LINKS



FORMULA

Prime[n]+m*(1+m)/2 is a prime for some m>0.


EXAMPLE

a(2)=4 because prime[2]+(1+2+3+4)=3+10=13 is a prime


MATHEMATICA

Flatten[(Sqrt[1+8#]1)/2&/@With[{trnos=Accumulate[Range[30]]}, Table[ Select[ trnos, PrimeQ[Prime[n]+#]&, 1], {n, 100}]]] (* Harvey P. Dale, Jun 12 2013 *)


CROSSREFS



KEYWORD

easy,nonn


AUTHOR



STATUS

approved



