25578

Appears in sequences

• a(n) = s(1)t(n) + s(2)t(n-1) + ... + s(k)t(n+1-k), where k = [ (n+1)/2 ], s = (odd natural numbers), t = A000201 (lower Wythoff sequence).at n=44A024599
• a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 5, with initial values 1,0,1,0.at n=17A025275
• Numbers which can be written as b^2*c^2*(b^2+c^2).at n=26A063663
• Numbers n such that sopf(sigma(n)) = sigma(sopf(n)), where sopf(x) = sum of the distinct prime factors of x.at n=34A076532
• Composite numbers such that the square root of the sum of squares of their prime factors is a prime.at n=13A134607
• Consider the base-8 Kaprekar map n->K(n) defined in A165090. Sequence gives numbers belonging to cycles, including fixed points.at n=15A165095
• Consider the base-8 Kaprekar map n->K(n) defined in A165090. Sequence gives numbers belonging to cycles of length greater than 1.at n=12A165097
• Triangle T(n,k) represents the coefficients of (x^9*d/dx)^n, where n=1,2,3,...;generalization of Stirling numbers of second kind A008277, Lah-numbers A008297.at n=33A223511
• Number of length n+7 0..2 arrays with at most one downstep in every 7 consecutive neighbor pairs.at n=5A255106
• Number of length n+6 0..2 arrays with at most one downstep in every n consecutive neighbor pairs.at n=6A255113
• Least number of consecutive primes beginning with 2, the sum of which (A007504) exceeds e^n.at n=22A323361
• G.f.: Sum_{n>=0} (n+1) * (x + x^n)^n.at n=77A325997
• Number of subsets of {1..n} containing no sums or products of distinct elements.at n=22A326024
• Primitive numbers that are the sum of the squares of two of their distinct divisors.at n=17A338485
• a(n) is the number of large or small squares that are used to tile primitive squares of type 1 whose length of side is A344333(n).at n=15A344334
• a(n) is the number of large or small squares that are used to tile primary squares of type 1 (see A344331) whose side length is A345285(n).at n=19A345286
• a(n) is the number of arch configuration solutions with n arches derived from 2 concentric arches using the exterior arch splitting algorithm.at n=11A354387
• Numbers k such that k - A224787(k) is a square.at n=18A386623
• Lower (1/2,1/3) midsequence of (n^2) and (n^3); see Comments.at n=42A389582
• Upper (1/2,1/3) midsequence of (n^2) and (n^3); see Comments.at n=42A389583