Hello Math-fun and Seqfan, N=325648 is interesting if read so: "3" means "a cube is visible in N" (yes, it is "8" -- 8=2*2*2) "2" means "a square is visible in N" (yes, it is "25" -- 25=5*5) (4 is ok too, being 2*2) "5" means "a power 5 is visible in N" (yes, it is "32" = 2*2*2*2*2) "6" means "a power 6 is visible in N" (yes, it is "64" = 2*2*2*2*2*2) "4" means "a power 4 is visible in N" (yes, it is "256" = 4*4*4*4*) "8" means "a power 8 is visible in N" (yes, it is "256" =2*2*2*2*2*2*2*2) N=832564 is a SPN too, of course. ["visible" means "as a whole": "25" is NOT visible in 235] Question: Can someone compute all such SPN _which don't include any 0's or 1's_ ? This restriction applies because 0^a=0 and 1^b=1, which brings a lot of unwan- ted SPN like 117 or 308: "1" means "a power 1 is visible in N" (yes, it is "1" -- 1^1=1) "7" means "a power 7 is visible in N" (yes, it is "1" again -- 1^7=1) or "3" means "a cube is visible in N" (yes, it is "0" -- 0*0*0=0) "0" means "a power 0 is visible in N" (yes, it is "0" again -- any a^0=0) "8" means "a power 8 is visible in N" (yes, it is "0" again and again -- 0^8=0) Best, É.