OFFSET
1,1
COMMENTS
Also primes of the form (2*n^3 - n^2 - n - 2)/2.
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..10000
EXAMPLE
a(2) = 109 since 5^3 - T(5) - 1 = 125 - 15 - 1 = 109, which is prime.
a(6) = 9029 since 21^3 - T(21) - 1 = 9261 - 231 - 1 = 9029 which is prime.
MAPLE
KD:= proc() local a, b, d; a:= n^3; b:=(1/2)*n*(n+1); d:=a-b-1; if isprime(d) then RETURN(d): fi; end: seq(KD(), n=1..500);
MATHEMATICA
Select[Table[(n^3) - (n/2*(n + 1)) - 1, {n, 200}], PrimeQ]
CROSSREFS
KEYWORD
nonn,less
AUTHOR
K. D. Bajpai, Oct 04 2013
STATUS
approved