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A232731
Number of numbers that yield an n-digit number after Reverse and Add!.
4
4, 50, 450, 4590, 45405, 454950, 4544550, 45454500, 454495500, 4545045000, 45449955000, 454500450000, 4544999550000, 45450004500000, 454499995500000, 4545000045000000, 45449999955000000, 454500000450000000, 4544999999550000000, 45450000004500000000
OFFSET
1,1
COMMENTS
A190481 is the number of distinct n-digit numbers after Reverse and Add!.
FORMULA
a(1) = A232729(1), a(n) = A232729(n) + A232730(n-1), n > 1.
From Colin Barker, Mar 20 2017: (Start)
G.f.: x*(4 + 10*x - 90*x^2 - 10*x^3 + 5*x^4) / ((1 - 10*x)*(1 - 10*x^2)).
a(n) = 10*a(n-1) + 10*a(n-2) - 100*a(n-3) for n>5.
(End)
MATHEMATICA
LinearRecurrence[{10, 10, -100}, {4, 50, 450, 4590, 45405}, 20] (* Harvey P. Dale, Sep 22 2017 *)
PROG
(PARI) Vec(x*(4 + 10*x - 90*x^2 - 10*x^3 + 5*x^4) / ((1 - 10*x)*(1 - 10*x^2)) + O(x^30)) \\ Colin Barker, Mar 20 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Lars Blomberg, Nov 29 2013
STATUS
approved