31721

Properties

Appears in sequences

• Prime quadruples: numbers k such that k, k+2, k+6, k+8 are all prime.at n=22A007530
• Primes at which the difference pattern X,2,4,2,Y (X and Y >= 6) occurs in A001223.at n=10A052165
• Primes p whose Zeckendorf-expansion A014417(p) is palindromic.at n=13A095730
• Primes p in prime quadruplets (p,p+2,p+6,p+8) at the end of maximal gaps in A113404.at n=7A113403
• 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, 1), (-1, 0, 1), (1, 0, 0), (1, 1, -1)}.at n=11A148136
• Coefficient of x in the reduction by x^2 -> x+2 of the polynomial p(n,x) defined below in Comments.at n=13A192425
• Prime numbers whose central digit equals the sum of the other digits.at n=25A235119
• Primes that can be generated by the concatenation in base 3, in ascending order, of two consecutive integers read in base 10.at n=40A287300
• a(n) equals the smallest Sophie Germain prime q such that pi_(p,2p+1)(q,10,(1,3)) - pi_(p,2p+1)(q,10,(3,1)) = n, where pi_(p,2p+1)(q,10,(b,c)) equals the number of Sophie Germain primes A005384(i) such A005384(i) <= q and (A005384(i),A005384(i+1)) == (b,c) (mod 10).at n=7A333084
• Lesser of twin primes (A001359) being both half-period primes (A097443).at n=31A347225
• Triangle read by rows: T(n,k) = number of j-covers of [n] with j<=k, k=1..2^n-1.at n=21A369950
• Prime numbersat n=3410