19513

Appears in sequences

• Tribonacci numbers: a(n) = a(n-1) + a(n-2) + a(n-3) for n >= 3 with a(0) = a(1) = 0 and a(2) = 1.at n=19A000073
• Hexagonal prism numbers: a(n) = (n + 1)*(3*n^2 + 3*n + 1).at n=18A005915
• Strong pseudoprimes to base 55.at n=9A020281
• Strong pseudoprimes to base 56.at n=12A020282
• Weight distribution of [79,40,15] binary quadratic-residue (or QR) code.at n=15A033869
• Sequence arising in search for Legendre sequences.at n=16A039795
• Consider all quadruples {a,b,c,d} which reach {k,k,k,k} in n steps under map {a,b,c,d}->{|a-b|,|b-c|,|c-d|,|d-a|}; look at max{a,b,c,d}; sequence gives minimal value of this.at n=26A045794
• Numbers k such that 281*2^k + 1 is prime.at n=22A053357
• Minimum value t such that all quadruples of Diffy_length >= n have a maximal value >= t.at n=28A065678
• a(n) = T(2n+1), where T(n) are the tribonacci numbers A000073.at n=9A073717
• a(n) = T(3n+1), where T(n) are tribonacci numbers A000073.at n=6A074581
• a(n) = ((1+(-1)^n)*T(n+1) + (1-(-1)^n)*S(n))/2, where T(n) = tribonacci numbers A000073, S(n) = generalized tribonacci numbers A001644.at n=18A075536
• a(n) is the sum of the (1,2)- and (1,3)-entries of the matrix P^n + T^n, where the 3 X 3 matrices P and T are defined by P = [0,1,0; 0,0,1; 1,0,0] and T = [0,1,0; 0,0,1; 1,1,1].at n=18A109523
• Expansion of -x^2*(x^9-x^8+2*x^7-x^6+x^5-2*x^4+x^2+1) / ((x^6-x^4+x^2+1) * (x^6+x^4+x^2-1)).at n=39A114952
• Numbers with sum of digits = 19, divisible by 19 and containing the string "19".at n=3A121669
• Tribonacci numbers A000073 which can be the hypotenuse of a Pythagorean triple.at n=4A130611
• Number of n X n binary arrays symmetric under 90 degree rotation with all ones connected only in a 0110-0100-1111 pattern in any orientation.at n=14A146797
• Products of three distinct happy primes A035497.at n=27A154717
• Members of A038512 of the form k, k+2, k+6, k+8.at n=29A155511
• a(n) = n*(2*n^2 + 5*n + 19)/2.at n=26A163675