115343360

Appears in sequences

• a(n) is the number of occurrences of 11s in the palindromic compositions of m=2*n-1 = the number of occurrences of 12s in the palindromic compositions of m=2*n.at n=21A079863
• Number of subsets of {1,.., n} containing exactly two primes.at n=31A089822
• a(n) = 4^n * n*(n+1).at n=10A116144
• Record values obtained in the iterative process related to the abundancy function sigma(n)/n described in comments.at n=21A247141