OFFSET
0,3
COMMENTS
A quasiperiodic function.
FORMULA
Sod_4 - sod_3 + sod_2 - sod_1 = sum(d(d-1)(d^2+1)), d's are digits of n
EXAMPLE
a(4) = 204 = 4(4-1)(4^2+1), a(5) = 520 = 5(5-1)(5^2+1).
MATHEMATICA
sod[n_]:=Module[{idn=IntegerDigits[n]}, Total[Total/@{-idn+idn^2-idn^3+idn^4}]]; Array[sod, 50, 0] (* Harvey P. Dale, Sep 20 2011 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Zak Seidov, Nov 01 2002
STATUS
approved