21653

Appears in sequences

• Discriminants of real quadratic fields with class number 1 and related continued fraction period length of 20.at n=30A050969
• Numbers k such that 2^k - prime(k) is prime.at n=20A078583
• Numbers k such that either 2^k + prime(k) or 2^k - prime(k) is prime.at n=44A130640
• Number of increasing sequences of n integers x(1),...,x(n) with values in 1..2*n such that x(j) divides x(k) if j divides k.at n=42A180384
• Number of strictly increasing arrangements of 4 nonzero numbers in -(n+2)..(n+2) with sum zero.at n=45A188123
• Number of (n+1)X(n+1) 0..1 arrays with every 2X2 subblock ne-sw antidiagonal difference nondecreasing horizontally and nw+se diagonal sum nondecreasing vertically.at n=6A258546
• Number of (n+1) X (7+1) 0..1 arrays with every 2 X 2 subblock ne-sw antidiagonal difference nondecreasing horizontally and nw+se diagonal sum nondecreasing vertically.at n=6A258553
• Number of (7+1) X (n+1) 0..1 arrays with every 2 X 2 subblock ne-sw antidiagonal difference nondecreasing horizontally and nw+se diagonal sum nondecreasing vertically.at n=6A258560
• Palindromic numbers in bases 2 and 8 written in base 10.at n=46A259380
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 302", based on the 5-celled von Neumann neighborhood.at n=41A271158
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 457", based on the 5-celled von Neumann neighborhood.at n=32A272282
• Fixed points of A275957; numbers n for which A060125(n) = A225901(n).at n=49A275843
• Breadth-first reading of the subtree rooted at 7 of the tree where each parent node is the arithmetic derivative (A003415) of all its children.at n=33A327977
• Numbers that are the sum of eight fourth powers in nine or more ways.at n=30A345584
• Numbers that are the sum of eight fourth powers in exactly nine ways.at n=15A345841
• Binary palindromic numbers whose digit sum and aliquot sum are also binary palindromic.at n=14A363965
• Number of integer partitions of n with more parts than distinct divisors of parts.at n=38A371171