19706

Appears in sequences

• a(n) = (3*5^n - 2*4^n + 3^n)/2.at n=6A083331
• Ulam's spiral (WSW spoke).at n=35A143854
• Minimal number (in decimal representation) with n nonprime substrings in base-3 representation (substrings with leading zeros are considered to be nonprime).at n=49A217103
• Expansion of Sum_{k>=1} phi(k) * x^k/(1 - x^k)^4, where phi = Euler totient function (A000010).at n=45A309323
• a(n) is the number of terms in the analog of A121805 but starting with n, or -1 if that sequence is infinite.at n=4A330128
• Numbers k at which point A336459(k) appears multiplicative, but A051027(k) does not.at n=34A336561
• Number T(n,k) of nodes in the k-th connected component of all endofunctions on [n] when components are ordered by increasing size; triangle T(n,k), n>=1, 1<=k<=n, read by rows.at n=17A350202
• a(n) is the number of terms in the analog of A121805 but starting with A037124(n), or -1 if that sequence is infinite.at n=4A367601