OFFSET
1,1
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
MathWorld, Pairing Function
PROG
(PARI)
A046523(n) = { my(f=vecsort(factor(n)[, 2], , 4), p); prod(i=1, #f, (p=nextprime(p+1))^f[i]); }; \\ This function from Charles R Greathouse IV, Aug 17 2011
for(n=1, 10000, write("b286255.txt", n, " ", A286255(n)));
(Scheme) (define (A286255 n) (* (/ 1 2) (+ (expt (+ (A046523 n) (A046523 (+ 1 n))) 2) (- (A046523 n)) (- (* 3 (A046523 (+ 1 n)))) 2)))
(Python)
from sympy import factorint
def T(n, m): return ((n + m)**2 - n - 3*m + 2)/2
def P(n):
f = factorint(n)
return sorted([f[i] for i in f])
def a046523(n):
x=1
while True:
if P(n) == P(x): return x
else: x+=1
def a(n): return T(a046523(n), a046523(n + 1)) # Indranil Ghosh, May 07 2017
CROSSREFS
Cf. A005383 (after its initial term 3, gives the positions of 23's in this sequence).
KEYWORD
nonn
AUTHOR
Antti Karttunen, May 07 2017
STATUS
approved