20211

Appears in sequences

• Rounded volume of a regular octahedron with edge length n.at n=35A071400
• Indices n of primes p(n), p(n+4) such that p(n)-1 and p(n+4)-1 have the same largest prime factor.at n=21A105407
• Self-convolution cube-root of A106216, which consists entirely of digits {0,1,2} after the initial terms {1,3}.at n=13A106219
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (-1, 0, 0), (0, -1, 1), (1, 0, -1), (1, 1, 1)}.at n=8A149684
• Number of 0..n arrays x(0..4) of 5 elements with zero 4th difference.at n=17A200156
• a(0) = 16, after which, if (2*a(n-1)) - 1 = product_{k >= 1} (p_k)^(c_k) then a(n) = product_{k >= 1} (p_{k-1})^(c_k), where p_k indicates the k-th prime, A000040(k).at n=23A246345
• Numbers n such that A002496(n) mod A002496(n-1) is a perfect square.at n=42A247592
• Self-slideable numbers: numbers which can reproduce themselves by sliding each digit d by d places either to the left or to the right.at n=50A295010
• Numbers of the form HMMSS with primes H < 24 and MM, SS < 60, for which the number of seconds after midnight, 3600*H+60*MM+SS, is also prime.at n=0A295011
• Prime time numbers on 6-digit clocks: numbers of the form HMMSS where H, MM, SS are primes, H < 24, MM and SS < 60.at n=4A295014
• Numbers with decimal expansion d_1, ..., d_w such that for any k in 1..w there is some m in 1..w such that d_k = d_m = abs(k - m).at n=20A336880
• Number of palindromes < 10^n whose squares are also palindromes.at n=42A343098