A002381 Numbers of the form (p^2 - 1)/120 where p is 1 or prime.

0, 1, 3, 7, 8, 14, 29, 31, 42, 52, 66, 85, 99, 143, 161, 185, 190, 267, 273, 304, 330, 371, 437, 476, 484, 525, 603, 612, 658, 806, 913, 1015, 1074, 1197, 1261, 1340, 1394, 1463, 1477, 1548, 1606, 1680, 1771, 1912, 2009, 2075, 2159, 2262, 2439, 2698, 2717

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Comments

For n>1, primes p corresponding to a(n) are in A038872(n) = A045468(n-1) = A141158(n). - Ray Chandler, Jul 29 2019

References

• H. Gupta, On a conjecture of Chowla, Proc. Indian Acad. Sci., 5A (1937), 381-384.
• N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Ray Chandler, Table of n, a(n) for n = 1..10000
• H. Gupta, On a conjecture of Chowla, Proc. Indian Acad. Sci., 5A (1937), 381-384. [Annotated scanned copy]

Crossrefs

Cf. A002382, A002855, A038872, A045468, A141158, subsequence of A093722.

Programs

Mathematica

Join[{0},Select[Table[(p^2-1)/120,{p,Prime[Range[200]]}],IntegerQ]] (* Harvey P. Dale, Jan 14 2020 *)

PARI

j=[]; for(n=0,150,x=prime(n)^2-1; if(Mod(x,120)==0,j=concat(j,(x/120)))); j

Extensions

More terms from Jason Earls, Jul 29 2001