21989

Appears in sequences

• a(n) = s(1)s(n) + s(2)s(n-1) + ... + s(k)s(n+1-k), where k = [ (n+1)/2 ], s = (1, p(1), p(2), ...).at n=30A024479
• Number of partitions of n that do not contain 3 as a part.at n=42A027337
• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 74 ones.at n=28A031842
• Composite numbers whose prime factors contain no digits other than 1 and 9.at n=18A036309
• Numbers k such that the smoothly undulating palindromic number (98*10^k - 89)/99 is a prime.at n=4A062232
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, 1, 1), (0, 1, -1), (1, 0, -1), (1, 1, 1)}.at n=8A149691
• Numbers k such that A383844(k) and A383844(k+1) are nonzero.at n=48A384310