OFFSET
1,2
COMMENTS
A member of the family of sequences defined by a(n) = Sum_{i=1..n}[i*c(1)*..*c(r)]^(i-1); c(i) integers. Here c(1)=1. - Ctibor O. Zizka, Feb 23 2008
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..100
FORMULA
a(n) = Sum_{k=1..n} k^(k-1).
a(n) = Sum_{k=1..n} A000169(k). - Jonathan Vos Post, Feb 12 2010
EXAMPLE
a(3) = 12 because the matrix is: 1,1,1 1,2,4 1,3,9 and the trace is 1+2+9 = 12.
1 = 1^0; 3 = 1^0 + 2^1; 12 = 1^0 + 2^1 + 3^2; 76 = 1^0 + 2^1 + 3^2 + 4^3.
MAPLE
a:=n-> sum((j+1)^j, j=0..n-1): seq(a(n), n=1..25); # Zerinvary Lajos, Dec 17 2008
MATHEMATICA
Table[Sum[i^(i-1), {i, n}], {n, 25}]
PROG
(PARI) { for (n=1, 100, write("b060946.txt", n, " ", sum(k=1, n, k^(k - 1))); ) } \\ Harry J. Smith, Jul 15 2009
(Magma) [(&+[j^(j-1): j in [1..n]]): n in [1..25]]; // G. C. Greubel, Apr 09 2021
(Sage) [sum(j^(j-1) for j in (1..n)) for n in (1..25)] # G. C. Greubel, Apr 09 2021
(Python)
from itertools import accumulate, count, islice
def A060946_gen(): # generator of terms
yield from accumulate((k**(k-1) for k in count(1)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Ahmed Fares (ahmedfares(AT)my-deja.com), May 08 2001
EXTENSIONS
More terms from Zak Seidov, Jul 07 2003
STATUS
approved