|
| |
|
|
A067692
|
|
a(n) = sum{d*t : 0<d<=t<=n and d|n and t|n}.
|
|
12
|
|
|
|
1, 7, 13, 35, 31, 97, 57, 155, 130, 227, 133, 497, 183, 413, 418, 651, 307, 988, 381, 1155, 762, 953, 553, 2225, 806, 1307, 1210, 2093, 871, 3242, 993, 2667, 1762, 2183, 1802, 5096, 1407, 2705, 2418, 5155, 1723, 5858
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,2
|
|
|
COMMENTS
|
For p prime: a(p) = 1+p+p^2, a(A000040(k))=A060800(k).
|
|
|
LINKS
|
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
|
|
|
FORMULA
|
a(n) = 1/2*(sigma_1(n)^2+sigma_2(n)), cf. A000203, A001157.
|
|
|
EXAMPLE
|
a(6) = 1*1+1*2+1*3+1*6+2*2+2*3+2*6+3*3+3*6+6*6 = 1+2+3+6+4+6+12+9+18+36 = 97.
|
|
|
PROG
|
(PARI) a(n)=my(D=sigma(n)); sumdiv(n, t, D-=t; t*(D+t)) \\ Charles R Greathouse IV, Aug 21 2011
(PARI) a(n)=(sigma(n)^2+sigma(n, 2))/2 \\ Charles R Greathouse IV, Aug 21 2011
|
|
|
CROSSREFS
|
Sequence in context: A061204 A060983 A001001 * A117706 A066673 A173230
Adjacent sequences: A067689 A067690 A067691 * A067693 A067694 A067695
|
|
|
KEYWORD
|
nonn,changed
|
|
|
AUTHOR
|
Reinhard Zumkeller, Feb 04, 2002
|
|
|
STATUS
|
approved
|
| |
|
|
