OFFSET
1,1
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10000
FORMULA
Sequence is 3*(distinct elements in A198385).
Numbers of the form 3*m^2 where 2*m^2 is in A004431. - Chai Wah Wu, Oct 05 2017
EXAMPLE
75 = 1^2 + 5^2 + 7^2 = 1 + 25 + 49, with 25 - 1 = 49 - 25 = 24.
675 = 3^2 + 15^2 + 21^2 = 9 + 225 + 441, with 225 - 9 = 441 - 225 = 216.
PROG
(PARI) t=4; k=3; while(t<=13000, i=k; e=0; v=t+i; while(i>1&&e==0, if(issquare(v), m=3*t; e=1; print1(m, ", ")); i+=-2; v+=i); k+=2; t+=k)
CROSSREFS
KEYWORD
nonn
AUTHOR
Antonio Roldán, Sep 14 2017
STATUS
approved