OFFSET
1,2
COMMENTS
a(58) = A000058(58) = 192523...920807 (58669977298272603 digits) is too large to include in the b-file. - Pontus von Brömssen, May 19 2022
Comment from N. J. A. Sloane, Dec 26 2022 (Start)
Note that a(n) = -1 can arise in two ways: either A_n has fewer than n terms, or A_n has at least n terms, but its n-th term is -1.
Here is a summary of the terms with n <= 80.
a(n) = -1 occurs just twice, for n = 53 and 54, in both cases because the relevant New York subway lines do not have enough stops.
a(1) though a(65) are known, although a(58) = = 192523...920807 has 58669977298272603 digits.
a(66) is the first unknown value.
Also unknown for n <= 80 are a(67), a(72), a(74), a(75), a(76), and a(77) (counts of numbers <= 2^n represented by various quadratic forms; some of these do not even have b-files), and a(80), which like a(66) is a graph-theory question. (End)
LINKS
Seth A. Troisi, Table of n, a(n) for n = 1..57 (terms 1..48 from Pontus von Brömssen).
N. J. A. Sloane, My favorite integer sequences, in Sequences and their Applications (Proceedings of SETA '98).
N. J. A. Sloane, "A Handbook of Integer Sequences" Fifty Years Later, arXiv:2301.03149 [math.NT], 2023, p. 21.
MAPLE
for m from 1 do
url:= sprintf("https://oeis.org/A%06d/b%06d.txt", m, m);
S:= URL:-Get(url);
L:= StringTools[Split](S, "\n");
for t in L do
g:= sscanf(t, "%d %d");
if nops(g) = 2 and g[1] = m then
a[m]:= g[2];
break
fi;
od;
if not assigned(a[m]) then break fi;
od:
seq(a[i], i=1..m-1); # Robert Israel, May 31 2015
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Robert G. Wilson v, Aug 23 2000
EXTENSIONS
Rechecked and 4 more terms added by N. J. A. Sloane, May 25 2005
a(36) and a(42) corrected and a(43) to a(46) added by Robert Israel, May 31 2015
Definition revised by N. J. A. Sloane, Nov 27 2016
STATUS
approved