OFFSET
0,1
LINKS
Harry Metrebian, Table of n, a(n) for n = 0..130
Dario Alejandro Alpern, Brilliant numbers
EXAMPLE
a(5)=13 because 10^5+13 = 100013 = 103*971 and a(6)=9 because (10^3+9)^2 = 1009^2. For n>0, a(2n) = A033873(n).
MATHEMATICA
NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; LengthBase10[n_] := Floor[ Log[10, n] + 1]; f[n_] := Block[{k = 0}, If[ EvenQ[n] && n > 1, NextPrim[ 10^(n/2)]^2 - 10^(n/2), While[fi = FactorInteger[10^n + k]; Plus @@ Flatten[ Table[ # [[2]], {1}] & /@ fi] != 2 || Length[ Union[ LengthBase10 /@ Flatten[ Table[ # [[1]], {1}] & /@ fi]]] != 1, k++ ]; k]]; Table[ f[n], {n, 0, 63}]
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Jason Earls, Jun 03 2003
EXTENSIONS
Edited and extended by Robert G. Wilson v, Jun 27 2003
STATUS
approved