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A225048
Numbers that cannot be expressed as n plus the sum of the squared digits of n for any integer n.
2
1, 3, 4, 5, 7, 8, 9, 10, 14, 15, 16, 18, 19, 21, 22, 25, 27, 28, 29, 32, 33, 34, 35, 37, 38, 40, 43, 46, 47, 48, 49, 50, 52, 55, 57, 60, 61, 63, 64, 65, 70, 71, 73, 74, 78, 79, 82, 84, 85, 88, 89, 91, 92, 93, 94, 97, 99, 100, 104, 106, 109, 110, 115, 120, 122
OFFSET
1,2
COMMENTS
A natural extension of the Self or Colombian numbers (A003052).
Up to 144, there are more numbers that cannot be expressed in this way than numbers that can. Thereafter, there are always more numbers that can.
EXAMPLE
26 is not in the sequence, because 21+2^2+1^2=26. However, no such solution exists for 25 or 27.
MATHEMATICA
nn=122; Complement[Range[nn], Table[n+Total[IntegerDigits[n]^2], {n, nn}]] (* Jayanta Basu, May 05 2013 *)
PROG
(R) digsqsum<-function(x) sum(as.numeric(unlist(strsplit(as.character(x), split="")))^2)
which(is.na(match(1:1000, 1:1000+sapply(1:1000, digsqsum)))
CROSSREFS
KEYWORD
nonn,base
STATUS
approved