login
A214963
a(0)=a(1)=1, a(n) = least k > a(n-1) such that k*a(n-2) is an oblong number.
4
1, 1, 2, 6, 10, 12, 21, 35, 36, 70, 112, 117, 230, 368, 390, 759, 763, 1290, 2244, 2292, 3133, 3580, 4170, 5154, 5355, 7014, 7710, 9160, 9328, 11592, 19274, 22616, 27555, 37290, 37312, 40756, 47820, 63680, 68862, 87450, 93730, 108985, 110262, 132888, 137731, 159159
OFFSET
0,3
MAPLE
isA002378 := proc(n)
if issqr(1+4*n) then
(sqrt(1+4*n)-1) /2 ;
type(%, 'integer') ;
else
false;
end if;
end proc:
A214963 := proc(n)
option remember;
local k ;
if n <= 1 then
1;
else
for k from procname(n-1)+1 do
if isA002378(k*procname(n-2)) then
return k;
end if;
end do:
end if;
end proc: # R. J. Mathar, Aug 10 2012
CROSSREFS
Cf. A002378.
Sequence in context: A373049 A071638 A028348 * A140776 A277238 A108783
KEYWORD
nonn
AUTHOR
Alex Ratushnyak, Aug 03 2012
STATUS
approved