23240

Appears in sequences

• a(n) = (2*n-1)*(13*n^2-13*n+6)/6.at n=17A063493
• Rectangular array read by antidiagonals: a(n, k) is the number of ways to put k labeled objects into n labeled boxes so that there is one box with exactly one object (n, k >= 1).at n=61A131104
• Numbers m such that m^2 + 3^k is prime for k = 1, 2, 3.at n=32A177173
• Number of partitions of n containing a clique of size 10.at n=46A183567
• For positive n with prime decomposition n = Product_{j=1..m} (p_j^k_j) define A_n = Sum_{j=1..m} (p_j*k_j) and B_n = Sum_{j=1..m} (p_j^k_j). This sequence gives those n for which A_n and B_n are both prime and B_n = A_n + 2 (i.e., form a twin prime pair).at n=40A185718
• Smallest multiple of n whose factorial digit sum equals n.at n=34A191895
• Number of cyclotomic cosets of 9 mod 10^n.at n=38A220020
• Numbers m such that the GCD of the x's that satisfy sigma(x) = m is 4.at n=24A241649
• a(n) = n*(n^2 + 3*n - 2)/2.at n=35A256857
• Numbers k such that card({x|sigma(x)=k}) > 1 and (Sum_{sigma(x)=k} x) < k.at n=27A258931
• Integers n such that n!/(n-2) + 1 is prime.at n=31A271376
• Numbers with property that both the digit sum and the sum of the prime factors (counted with multiplicity) have only digits 0 and 1 in base 10.at n=19A297614
• E.g.f.: exp(1 / (1 - arcsinh(x)) - 1).at n=7A331616