%I A161707
%S A161707 1,3,7,21,53,111,203,337,521,763,1071,1453,1917,2471,3123,3881,4753,
%T A161707 5747,6871,8133,9541,11103,12827,14721,16793,19051,21503,24157,27021,
%U A161707 30103,33411,36953,40737,44771,49063,53621,58453,63567,68971,74673
%N A161707 (4*n^3 - 9*n^2 + 11*n + 3)/3.
%C A161707 {a(k): 0 <= k < 4} = divisors of 21:
%C A161707 a(n) = A027750(A006218(20) + k + 1), 0 <= k < A000005(21).
%H A161707 R. Zumkeller, <a href="a161700.txt">Enumerations of Divisors</a>
%F A161707 a(n) = C(n,0) + 2*C(n,1) + 2*C(n,2) + 8*C(n,3).
%e A161707 Differences of divisors of 21 to compute the coefficients of their interpolating 
               polynomial, see formula:
%e A161707 1 ... 3 ... 7 ... 21
%e A161707 .. 2 ... 4 .. 14
%e A161707 ..... 2 .. 10
%e A161707 ........ 8.
%Y A161707 A005408, A000124, A016813, A086514, A000125, A058331, A002522, A161701, 
               A161702, A161703, A000127, A161704, A161706, A161708, A161710, A080856, 
               A161711, A161712, A161713, A161715, A006261.
%Y A161707 Sequence in context: A036569 A018303 A098545 this_sequence A151267 A091489 
               A047087
%Y A161707 Adjacent sequences: A161704 A161705 A161706 this_sequence A161708 A161709 
               A161710
%K A161707 nonn
%O A161707 0,2
%A A161707 Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 17 2009