OFFSET
1,1
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
Eric Weisstein's World of Mathematics, Pairing Function
PROG
(PARI)
A000203(n) = sigma(n);
for(n=1, 10000, write("b286359.txt", n, " ", A286359(n)));
(Scheme) (define (A286359 n) (* (/ 1 2) (+ (expt (+ (A000203 n) (A000203 (* 2 n))) 2) (- (A000203 n)) (- (* 3 (A000203 (* 2 n)))) 2)))
(Python)
from sympy import divisor_sigma as D
def T(n, m): return ((n + m)**2 - n - 3*m + 2)/2
def a(n): return T(D(n), D(2*n)) # Indranil Ghosh, May 12 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 10 2017
STATUS
approved