21676

Appears in sequences

• Numbers k such that 17*2^k - 1 is prime.at n=28A001774
• Expansion of (1+3*x^2+7*x^3+15*x^4+13*x^5+15*x^6+8*x^7+4*x^8)/((1-x)*(1-x^2)^3*(1-x^3)^2).at n=18A037241
• Base-2 logarithm of (n-th even superperfect number divided by 2^n), plus 1.at n=24A134713
• Number of n X n arrays of squares of integers, symmetric about main diagonal, with all rows summing to 50.at n=3A156512
• Triangle read by rows: T(n,k) is the number of up-down permutations of {1,2,...,n} having genus k (see first comment for definition of genus).at n=67A178516
• Numbers k such that k!!! - 3^k is prime.at n=29A261316
• Positive integers that have exactly ten representations of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.at n=19A317400