OFFSET
1,1
COMMENTS
Here we are considering powerful numbers (first definition) A001694. Note that, by definition, 1 is powerful.
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..120
Eric Weisstein's World of Mathematics, Powerful Number.
EXAMPLE
a(2)=17, since 17 = 16+1 = 8+9.
MATHEMATICA
pwfQ[n_] := n == 1 || Min[Transpose[FactorInteger@n][[2]]] > 1; lim=200000; pt = Select[Range[lim], pwfQ]; t = Table[0, {i, lim}]; Do[v = pt[[i]]+ pt[[j]]; If[v<=lim, t[[v]]++ ], {i, Length@pt}, {j, i}]; Table[Position[t, k][[1, 1]], {k, 22}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Giovanni Resta, Jan 21 2006
EXTENSIONS
a(23)-a(35) from Donovan Johnson, Dec 07 2008
STATUS
approved