20158

Appears in sequences

• a(1) = 1; a(n+1) = sum of terms in continued fraction for the sum of the continued fractions, [a(1); a(2), a(3),...,a(n-1),a(n)] and [a(n); a(n-1), a(n-2),...,a(2), a(1)].at n=18A058081
• Number of permutations of length n which avoid the patterns 1234, 3421, 4312.at n=31A116756
• G.f. satisfies: A(x) = 1 + x*A(x)^3*A(x*A(x)^3).at n=6A215505
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 619", based on the 5-celled von Neumann neighborhood.at n=25A273252
• Solution of the complementary equation a(n) = 3*a(n-2) + b(n-2), where a(0) = 1, a(1) = 2, b(0) = 3, b(1) = 4, and (a(n)) and (b(n)) are increasing complementary sequences.at n=16A295139
• Numbers k such that k divides the sum of digits in factorial base of all numbers from 1 to k.at n=21A333702
• The smallest number such that n or more numbers k exist with k - a(n) = sopfr(k) + sopfr(a(n)), where sopfr(m) is the sum of the primes dividing m with repetition.at n=10A370352
• a(n) is the smallest number such that exactly n numbers k exist with k - a(n) = sopfr(k) + sopfr(a(n)), where sopfr(m) is the sum of the primes dividing m with repetition.at n=10A370356