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A015506 a(1)=1, a(n) = sum_{k=1}^{k=n-1} (5^k-1)/4 a(k). 0
1, 1, 7, 224, 35168, 27501376, 107447876032, 2098671914657024, 204950003169660992768, 100073397447688408870744576, 244319893042568615235897903058432, 2982420752607212448380293251367177293824 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..12.

FORMULA

a(n) = ((5^(n-1) + 3)/4) * a(n-1). - Vincenzo Librandi, Nov 12 2012

PROG

(MAGMA) I:=[1, 1, 7]; [n le 3 select I[n] else ((5^(n-1) + 3)/4) * Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 12 2012

CROSSREFS

Sequence in context: A302059 A138247 A322709 * A210099 A193503 A303533

Adjacent sequences:  A015503 A015504 A015505 * A015507 A015508 A015509

KEYWORD

nonn,easy

AUTHOR

Olivier Gérard

STATUS

approved

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Last modified May 28 17:37 EDT 2020. Contains 334684 sequences. (Running on oeis4.)