OFFSET
0,5
COMMENTS
LINKS
Ilya Gutkovskiy, Extended graphical example
Ilya Gutkovskiy, Extended graphical example for additional conjecture
Eric Weisstein's World of Mathematics, Palindromic Number
Eric Weisstein's World of Mathematics, Squarefree
FORMULA
G.f.: (Sum_{k>=1} x^A071251(k))^3.
EXAMPLE
a(22) = 6 because we have [11, 6, 5], [11, 5, 6] [6, 11, 5], [6, 5, 11], [5, 11, 6] and [5, 6, 11].
MATHEMATICA
nmax = 85; CoefficientList[Series[Sum[Boole[SquareFreeQ[k] && PalindromeQ[k]] x^k, {k, 1, nmax}]^3, {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Ilya Gutkovskiy, Feb 19 2017
STATUS
approved