20347

Properties

Appears in sequences

• Number of (n,3,7) difference families over Z_n.at n=6A011997
• Decimal part of cube root of a(n) starts with 3: first term of runs.at n=25A034129
• Second member of a sexy prime quadruple: value of p+6 such that p, p+6, p+12 and p+18 are all prime.at n=35A046122
• Discriminants of imaginary quadratic fields with class number 25 (negated).at n=34A056987
• The array in A059216 read by antidiagonals in 'up' direction.at n=37A059217
• The array in A059216 read by antidiagonals in the direction in which it was constructed.at n=43A059234
• Luhn primes: primes p such that p + (p reversed) is also a prime.at n=36A061783
• Initial term in sequence of four consecutive primes separated by 3 consecutive differences each <=6 (i.e., when d=2,4 or 6) and forming d-pattern=[6, 4,2]; short d-string notation of pattern = [642].at n=25A078855
• Number of permutations satisfying -k<=p(i)-i<=r and p(i)-i not in I, i=1..n, with k=1, r=5, I={1,4}.at n=21A079961
• Numbers p such that p = (prime(n)+ prime(n+2))/2 is prime for prime indices n=2, 3, 5...at n=22A098038
• Primes congruent to 51 mod 59.at n=36A142778
• Primes congruent to 34 mod 61.at n=34A142832
• Beginnings of maximal chains of primes with five members (four links).at n=5A152868
• Primes p such that p^3 - 24 and p^3 + 24 are also primes.at n=34A153323
• Primes p such that (p-1)*p*(p+1)-p+2 and (p-1)*p*(p+1)+p-2 are primes.at n=30A154944
• Number of n X 5 1..2 arrays containing at least one of each value, all equal values connected, rows considered as a single number in nondecreasing order, and columns considered as a single number in nondecreasing order.at n=15A166808
• Primes p such that 5*p+2, 7*p+4 and 11*p+6 are also prime.at n=23A173880
• Prime-generating polynomial: a(n) = 16*n^2 - 300*n + 1447.at n=45A181973
• Number of nondecreasing arrangements of 10 numbers in 0..n with the last equal to n and each after the second equal to the sum of one or two of the preceding four.at n=39A189333
• Let A = A025584. a(n) is the smallest A(m) such that the interval (A(m)*n, A(m+1)*n) contains no primes from A.at n=9A207820