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A161703 (4n^3 - 12n^2 + 14n + 3)/3. 17
1, 3, 5, 15, 41, 91, 173, 295, 465, 691, 981, 1343, 1785, 2315, 2941, 3671, 4513, 5475, 6565, 7791, 9161, 10683, 12365, 14215, 16241, 18451, 20853, 23455, 26265, 29291, 32541, 36023, 39745, 43715, 47941, 52431, 57193, 62235, 67565, 73191, 79121 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

{a(k): 0 <= k < 4} = divisors of 15:

a(n) = A027750(A006218(14) + k + 1), 0 <= k < A000005(15).

LINKS

Table of n, a(n) for n=0..40.

R. Zumkeller, Enumerations of Divisors

Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).

FORMULA

a(n) = C(n,0) + 2*C(n,1) + 8*C(n,3).

G.f.: (1-x-x^2+9*x^3)/(1-x)^4. [Colin Barker, Jan 08 2012]

EXAMPLE

Differences of divisors of 15 to compute the coefficients of their interpolating polynomial, see formula:

1 ... 3 ... 5 ... 15

.. 2 ... 2 .. 10

..... 0 ... 8

........ 8.

PROG

(MAGMA)[(4*n^3 - 12*n^2 + 14*n + 3)/3: n in [0..50]]; [From Vincenzo Librandi, Dec 27 2010]

(PARI) a(n)=n*(4*n^2-12*n+14)/3+1 \\ Charles R Greathouse IV, Sep 24 2015

CROSSREFS

Cf. A005408, A000124, A016813, A086514, A000125, A058331, A002522, A161701, A161702, A000127, A161704, A161706-A161708, A161710, A080856, A161711-A161713, A161715, A006261.

Sequence in context: A148503 A236571 A145939 * A018551 A103425 A119472

Adjacent sequences:  A161700 A161701 A161702 * A161704 A161705 A161706

KEYWORD

nonn,easy

AUTHOR

Reinhard Zumkeller, Jun 17 2009

STATUS

approved

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Last modified May 23 06:21 EDT 2017. Contains 286909 sequences.