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A114951 Numbers n such that the sum of the n-th triangular number and the n-th prime is prime. 1
1, 3, 4, 11, 15, 19, 20, 23, 24, 32, 39, 48, 51, 60, 67, 68, 71, 75, 83, 84, 88, 95, 100, 104, 111, 119, 120, 127, 132, 135, 143, 147, 168, 180, 183, 191, 195, 200, 203, 204, 207, 211, 212, 219, 236, 240, 243, 251, 252, 255, 275, 276, 284 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

EXAMPLE

The 11th triangular number is 66, the 11th prime is 31.

Their sum is 97, a prime. Therefore 11 is in the sequence.

MATHEMATICA

Select[Range[500], PrimeQ[ #*(# + 1)/2 + Prime[ # ]] &]

PROG

(PARI) list(lim)=my(v=List(), n); forprime(p=2, , if(n++>lim, break); if(isprime(n*(n+1)/2+p), listput(v, n))); Vec(v) \\ Charles R Greathouse IV, Jun 13 2017

CROSSREFS

Cf. A000217.

Sequence in context: A295067 A263262 A249650 * A085368 A041405 A042483

Adjacent sequences:  A114948 A114949 A114950 * A114952 A114953 A114954

KEYWORD

nonn,less

AUTHOR

J. M. Bergot, Jun 23 2007

EXTENSIONS

Edited and extended by Stefan Steinerberger and Robert G. Wilson v, Jun 24 2007

STATUS

approved

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Last modified December 16 09:06 EST 2019. Contains 330020 sequences. (Running on oeis4.)