OFFSET
1,1
COMMENTS
Corresponding numbers m such that m^2 = a(n) are listed in A136360.
Note that some numbers in A136360 are also perfect squares. The corresponding numbers k such that m = k^2 are listed in A136361.
Includes all nonzero members of A099764: this occurs when the two pentagonal pyramidal numbers are both equal to i^2*(i+1)/2 where i+1 is a square. - Robert Israel, Feb 04 2020
LINKS
Robert Israel, Table of n, a(n) for n = 1..985
FORMULA
a(n) = A136360(n)^2.
EXAMPLE
MAPLE
N:= 200: # for terms up to N^2*(N+1)/2.
PP:= [seq(i^2*(i+1)/2, i=1..N)]:
PP2:= sort(convert(select(`<=`, {seq(seq(PP[i]+PP[j], j=i..N), i=1..N)}, PP[-1]), list)):
select(issqr, PP2); # Robert Israel, Feb 04 2020
MATHEMATICA
Select[ Intersection[ Flatten[ Table[ i^2*(i+1)/2 + j^2*(j+1)/2, {i, 1, 300}, {j, 1, i} ] ] ], IntegerQ[ Sqrt[ # ] ] & ]
CROSSREFS
KEYWORD
nonn
AUTHOR
Alexander Adamchuk, Dec 25 2007
STATUS
approved