202020

Appears in sequences

• Ninth column (k=8) of sextinomial array A063260.at n=12A063263
• Łukasiewicz words for the rooted plane binary trees (interpretation d in Stanley's exercise 19) with the last leaf implicit, i.e., these words are given without the last trailing zero, except for the null tree which is encoded as 0.at n=4A071152
• Integers which have more than one coprime factorization into nonprime powers which sum to the same number.at n=25A072940
• Triplets: base 10 representation is the juxtaposition of three identical strings.at n=19A074842
• Smallest multiple of n using all digits of (n-1) with the same frequency and no others; or 0 if no such number exists.at n=20A083959
• a(n) = (n+1)*(n+2)*(n+3)*(n+4)*(19*n^2 + 47*n + 30)/720.at n=12A108677
• Triangle: q=3; m=2; t(n,k)=If[m == 0, n!, Product[Sum[(-1)^i*StirlingS2[ k - 1, i]*(m + 1)^i, {i, 0, k - 1}], {k, 1, n}]]; b(n,k,m)=If[n == 0, 1, t[n, m]/(t[k, m]*t[n - k, m])].at n=40A156594
• Any two consecutive digits in the sequence sum up to a prime.at n=45A158652
• a(n) = 3*(n + 1)*(n + 2)*(3*n + 1)*(3*n + 4)/4.at n=12A268685
• a(n) = 1*2*3 + 4*5*6 + 7*8*9 + 10*11*12 + 13*14*15 + 16*17*18 + ... + (up to n).at n=38A319014
• a(n) = 3*2*1 + 6*5*4 + 9*8*7 + 12*11*10 + ... + (up to the n-th term).at n=38A319867
• Self-stuffable numbers (see the Comments section for definition).at n=9A322323