100168domain: NAppears in sequencesa(n) = Sum_{i=0..n} A047130(i, n-i).at n=18A047131Number of permutations of length n which avoid the patterns 1234, 1243, 3241.at n=11A116839Number of times the digit 2 appears in the first 10^n digits of Catalan's constant.at n=5A224696