21018

Appears in sequences

• [ (4th elementary symmetric function of S(n))/(2nd elementary symmetric of S(n)) ], where S(n) = {3,4, ..., n+5}.at n=27A024194
• Index of first occurrence of n in A154404.at n=40A154952
• Array T(n,k) read by antidiagonals: T(n,k) is the number of [n,k]-triangulations in the plane, n >= 0, k >= 0.at n=48A169808
• Sequence of the "Natural Jewels": a natural jewel is a number that is totally enclosed by prime numbers in a version of Ulam Spiral.at n=16A172294
• Numbers n such that n is the average of four consecutive primes n-5, n-1, n+1 and n+5.at n=36A258088
• Number of entries in the eighth cycles of all permutations of [n].at n=3A285236
• Numbers k > 0 such that either 3*k+4, k-2, k+2, n+k or 3*k+5, k-1, k+1, k+5 are all primes.at n=46A290130
• Numbers k such that A335579(k) is divisible by at least one of the composites between prime(k) and prime(k+1).at n=11A335580
• Numbers on the square spiral board that are enclosed by four primes.at n=17A341542
• Number of Schroeder paths of semilength n up to reversal.at n=8A378939