21471

Appears in sequences

• Numbers k such that prime(k) == 1 (mod sigma(k)).at n=13A067697
• Sums of members of groups in A076063.at n=34A076066
• Sequence of which A078783 is the Recamán transform.at n=41A117073
• a(n) = Sum_{i=0..n} Sum_{j=0..n} (-1)^(i+j) * (i+j)!/(i!j!).at n=9A120305
• Odd composite numbers such that the sum of any two terms, plus 1, is a prime.at n=8A133762
• Integers of the form 8k + 7 that can be written as a sum of four distinct squares of the form m, m + 2, m + 3, m + 4, where m == 2 (mod 4).at n=17A243581
• E.g.f. A(x) satisfies: d/dx A(x) = 1 + A(x*exp(-x)).at n=7A307135
• Number of integer partitions with sum < n whose distinct parts cannot be linearly combined using all positive coefficients to obtain n.at n=50A365323
• Expansion of (1/x) * Series_Reversion( x * (1-x) * (1-x-x^5) ).at n=7A368933
• Number of integer partitions of n such that it is not possible to choose a different prime factor of each part.at n=37A370593