19495

Appears in sequences

• Composite numbers whose prime factors contain no digits other than 5 and 7.at n=28A036320
• Numbers k such that 7*10^k + 5*R_k - 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=9A103061
• A137576((k-1)/2) for composite numbers k from A141229.at n=4A140197
• 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, 1), (-1, 0, 1), (0, 1, -1), (1, -1, -1), (1, 1, 1)}.at n=8A149610
• a(n) = 54*n^2 + 1.at n=19A158646
• Number of partitions p of n such that max(p) - 3*min(p) is a part of p.at n=43A238627
• Numbers n such that n, p=prime(n) and q=prime(p) have the same sum of digits.at n=33A261142
• Composite numbers k such that k-1 divides 2^k-2.at n=23A330382
• a(n) = Sum_{1 <= x_1, x_2, x_3 <= n} sigma( ( n/gcd(x_1, x_2, x_3, n) )^2 ).at n=6A373131
• Number of integer compositions of n whose leaders of maximal anti-runs are not identical.at n=16A374640