A242384 Lesser of consecutive primes whose sum is of the form k*(k+2), for some integer k.

3, 11, 59, 139, 179, 311, 419, 541, 919, 1399, 1621, 2111, 3119, 5099, 6379, 8059, 8839, 9377, 15661, 16007, 16741, 17107, 21011, 21839, 23539, 24419, 28081, 30011, 31489, 33533, 35617, 37811, 39461, 41759, 44699, 45293, 60899, 68819, 71059, 78007, 83639, 84457, 86111

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..500

Example

311 is in the sequence because 311 is prime, nextprime(311)=313, and 311+313 = 624 = 24*(24+2).

Mathematica

Select[Partition[Prime[Range[9000]], 2, 1], IntegerQ[Sqrt[1+Total[#]]-1]&] [[All, 1]] (* Harvey P. Dale, May 15 2017 *)

Prog

(PARI) {k=2; while(k<10^5, l=nextprime(k+1); if(issquare(k+l+1), print1(k, ", ")); k=l)}

Crossrefs

Cf. A242383, A242385.

Sequence in context: A137690 A107007 A199854 * A225809 A267607 A319248

Adjacent sequences: A242381 A242382 A242383 * A242385 A242386 A242387

Keyword

nonn

Author

Antonio Roldán, May 12 2014

Status

approved