21506

Appears in sequences

• a(0) = 1, a(n) = 21*n^2 + 2 for n>0.at n=32A010011
• Semiprimes in A056105.at n=33A113519
• Triangle read by rows: A007318^(-1) * A136536.at n=73A136537
• Triangle read by rows: A007318^(-1) * A136536.at n=74A136537
• Number of 4 X n 0..1 arrays with rows and antidiagonals unimodal and columns nondecreasing.at n=9A224148
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 838", based on the 5-celled von Neumann neighborhood.at n=45A273681
• Markoff spectrum N^(5)(Lambda).at n=27A293173
• Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-1) + b(n-2) - b(n-3), where a(0) = 1, a(1) = 3, a(2) = 5, b(0) = 2, b(1) = 4, b(2) = 6, and (a(n)) and (b(n)) are increasing complementary sequences.at n=17A295358
• Positive integers k such that (k+1)^4 has a divisor congruent to -1 modulo k.at n=43A350916
• a(0) = 1, a(1) = 2, and a(n) = 23*a(n-1) - a(n-2) - 4 for n >= 2.at n=4A350917
• Expansion of Sum_{k>0} x^(3*k)/(1+x^k)^4.at n=50A363617
• Expansion of Sum_{n>=1} x^(n^2)*((1+x)/(1-x))^n.at n=32A369424