20681

Properties

Appears in sequences

• Primes that remain prime through 2 iterations of function f(x) = 8x + 1.at n=34A023260
• Number of 4-element intersecting families (with not necessarily distinct sets) of an n-element set.at n=5A052389
• Prime number spiral (clockwise, South spoke).at n=24A054566
• Sum of a(n) terms of 1/k^(5/6) first exceeds n.at n=26A056181
• a(n) is the least prime not already used such that the frequencies of the decimal digits in the first n terms are almost equal, i.e., for any two digits, their numbers of occurrences differ by no more than 1.at n=31A110457
• a(n) = (A112565(n) - 1)/n for n>=1.at n=8A112566
• Primes congruent to 31 mod 59.at n=40A142758
• Primes congruent to 2 mod 61.at n=38A142800
• Prime numbers q of primitive Pythagorean triangles such that perimeters are averages of twin prime pairs, p+1=q(prime), a=q^2-p^2, c=q^2+p^2, b=2*p*q, ar=a*b/2; s=a+b+c, s-+1 are primes.at n=32A155187
• Primes p such that p-1 and p+1 each contain at least one cubed prime in their prime factorization.at n=31A162870
• Number of distinct values taken by 7th derivative of x^x^...^x (with n x's and parentheses inserted in all possible ways) at x=1.at n=13A215796
• Primes of the form p*q - 30, where p and q are consecutive primes.at n=16A229613
• Non-palindromic balanced primes in base 2.at n=39A256081
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 806", based on the 5-celled von Neumann neighborhood.at n=44A273608
• Number of partitions of n such that the (sum of distinct even parts) = floor(n/2).at n=55A284610
• a(n) = 2*a(n-1) - a(n-2) + a([n/2]), where a(0) = 1, a(1) = 1, a(2) = 1.at n=33A298414
• Primes p such that the base-10 concatenations (p+1)||p and (p+1)||(p+1)||p are both prime.at n=40A309749
• Prime numbersat n=2329