login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A016161 Expansion of 1/((1-5x)(1-7x)). 5
1, 12, 109, 888, 6841, 51012, 372709, 2687088, 19200241, 136354812, 964249309, 6798573288, 47834153641, 336059778612, 2358521965909, 16540171339488, 115933787267041, 812299450322412, 5689910849522509 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Also, this is the number of incongruent integer-edged Heron triangles whose circumdiameter is the product of n distinct primes each of shape 4k + 1. Cf. A003462, A109021. - R. K. Guy, Jan 31 2007

LINKS

Table of n, a(n) for n=0..18.

Index entries for linear recurrences with constant coefficients, signature (12,-35).

FORMULA

a(n) = (7^(n+1)-5^(n+1))/2 = A081200(n+1). Binomial transform of A080962. - R. J. Mathar, Sep 18 2008

a(n) = 7*a(n-1) + 5^n. - Vincenzo Librandi, Feb 09 2011

PROG

(PARI) Vec(1/((1-5*x)*(1-7*x))+O(x^99)) \\ Charles R Greathouse IV, Sep 24 2012

CROSSREFS

Sequence in context: A011999 A128877 A085797 * A081200 A016214 A037581

Adjacent sequences:  A016158 A016159 A016160 * A016162 A016163 A016164

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified November 21 22:32 EST 2017. Contains 295054 sequences.