21957

Appears in sequences

• Numbers k such that 31*2^k-1 is prime.at n=24A050541
• a(n) = n^3 + 5.at n=28A084381
• 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, 0, -1), (1, 0, -1), (1, 1, 1)}.at n=8A149690
• Last term where no prime sums occur in A161190 in a 4-diagonal set of 24 terms.at n=11A161193
• Number of (n+1)X(4+1) 0..1 arrays x(i,j) with row sums sum{x(i,j), j=1..4+1} nondecreasing, and column sums sum{i^2*x(i,j), i=1..n+1} nondecreasing.at n=3A233300
• T(n,k)=Number of (n+1)X(k+1) 0..1 arrays x(i,j) with row sums sum{x(i,j), j=1..k+1} nondecreasing, and column sums sum{i^2*x(i,j), i=1..n+1} nondecreasing.at n=24A233301
• Number of (4+1) X (n+1) 0..1 arrays x(i,j) with row sums sum{x(i,j), j=1..n+1} nondecreasing, and column sums sum{i^2*x(i,j), i=1..4+1} nondecreasing.at n=3A233304
• a(n) is the smallest integer >= a(n-1) such that prime(n)*2^a(n)-1 is a prime number.at n=10A258868
• Expansion of 1/(1 - Sum_{k>=2} floor(bigomega(k)/2)*floor(2/bigomega(k))*x^k), where bigomega(k) is the number of prime divisors of k counted with multiplicity (A001222).at n=53A280238
• Expansion of Product_{k>=1} 1/(1 - x^k)^(k-phi(k)), where phi() is the Euler totient function (A000010).at n=30A307705
• Numbers that are the sum of eight fourth powers in nine or more ways.at n=34A345584
• Numbers that are the sum of eight fourth powers in ten or more ways.at n=16A345585
• a(n) = number of subsets S of {1,2,...,n} having more than 1 element such that (difference between least two elements of S) = difference between greatest two elements of S.at n=16A357282