23478

Appears in sequences

• a(1) = 1, a(2) = 2; for n >= 2, a(n+1) = a(n) + sum of the unique prime factors of a(n).at n=33A096460
• Numbers n such that the denominator of the 2n-th Bernoulli number is divisible by n but sum_{d|n} sigma(d)/phi(d) is not an integer.at n=14A099008
• Numbers n such that n divides the denominator of 2n-th Bernoulli number.at n=38A106741
• Numbers n such that n^4 divides 19^(n^2)-1.at n=8A127315
• Numbers k which can be split into two numbers x and y such that x^3 + y^2 is a multiple of k.at n=35A162451
• a(n) = 13*n*(n+1).at n=42A173307
• Total number of parts of multiplicity 4 in all partitions of n.at n=41A222704
• Numbers k such that card({x|sigma(x)=k}) > 1 and (Sum_{sigma(x)=k} x) < k.at n=28A258931
• Least positive integer k such that k*n+1 = prime(p) and k^2*n+1 = prime(q) for some pair of primes p and q.at n=43A261437
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 94", based on the 5-celled von Neumann neighborhood.at n=42A270135
• a(n) = Sum_{k=0..(n-1)/2} (n+2-k)*binomial(n-1-k,k).at n=17A271785
• a(n) is the number of partitions of n with Durfee square of size <= 3.at n=42A330641
• a(n) = Sum_{k=1..n} k * floor(n/k)^3.at n=24A350108
• First index k where A366574(k) = n.at n=26A366724
• Products of 5 distinct primes that are sandwiched between squarefree semiprime numbers.at n=20A376949
• Smallest positive number divisible by n that has n letters in US English, or 0 if none exists.at n=39A384131