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A107584 a(n) = 4^n - 4*n. 8
1, 0, 8, 52, 240, 1004, 4072, 16356, 65504, 262108, 1048536, 4194260, 16777168, 67108812, 268435400, 1073741764, 4294967232, 17179869116, 68719476664, 274877906868, 1099511627696, 4398046511020, 17592186044328, 70368744177572, 281474976710560, 1125899906842524 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Numbers a(n)=k such that number m with n 4's and k 1's has digit product = digit sum = 4^n.

LINKS

Table of n, a(n) for n=0..25.

Index entries for linear recurrences with constant coefficients, signature (6,-9,4).

FORMULA

a(0)=1, a(1)=0, a(2)=8, a(n) = 6*a(n-1) - 9*a(n-2) + 4*a(n-3). - Harvey P. Dale, Oct 21 2011

G.f.: (-17*x^2+6*x-1)/((x-1)^2*(4 x-1)). - Harvey P. Dale, Oct 21 2011

EXAMPLE

Corresponding numbers m are 1, 4, 1111111144, ...

MATHEMATICA

Table[4^m-4*m, {m, 0, 20}]

LinearRecurrence[{6, -9, 4}, {1, 0, 8}, 30] (* Harvey P. Dale, Oct 21 2011 *)

PROG

(MAGMA) [(4^n - 4*n): n in [0..25]]; // Vincenzo Librandi, Dec 16 2010

(PARI) a(n)=4^n-4*n \\ Charles R Greathouse IV, Sep 08 2012

CROSSREFS

Cf. A107583, A107585.

Sequence in context: A026973 A244718 A303509 * A323940 A027225 A073377

Adjacent sequences:  A107581 A107582 A107583 * A107585 A107586 A107587

KEYWORD

nonn,easy

AUTHOR

Zak Seidov, May 16 2005

EXTENSIONS

More terms from Vincenzo Librandi, Dec 16 2010

Corrected by Charles R Greathouse IV, Sep 08 2012

STATUS

approved

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Last modified September 19 12:57 EDT 2019. Contains 327198 sequences. (Running on oeis4.)