18019

Appears in sequences

• Pseudoprimes to base 95.at n=41A020223
• Strong pseudoprimes to base 95.at n=8A020321
• Numerators of continued fraction convergents to sqrt(439).at n=4A041836
• Number of steps in all Schroeder paths (i.e., consisting of steps U=(1,1), D=(1,-1),H=(2,0) and never going below the x-axis) from (0,0) to (2n,0).at n=5A089164
• Semiprimes in A003215.at n=32A113530
• a(n) = (n^3)/2 + (3*n^2)/2 + 3*n + 3.at n=31A127873
• E.g.f. satisfies A(x) = exp(x*A(x^6/6!)).at n=13A143570
• E.g.f. satisfies A(x) = exp(x*A(x^8/8!)).at n=14A143572
• a(n) = 12*n^2 + 18*n + 7.at n=38A154105
• a(n) = 25*n^3 - n*(5*n+1)/2 + 1.at n=8A167467
• Place a(n) blue and b(n) (A180002) red balls in an urn, draw 5 balls without replacement; Probability(5 red balls) = Probability(3 red and 2 blue balls).at n=9A180003
• Number of -n..n circular arrays x(0..5) of 6 elements with zero sums of x(i) and x(i)*x((i+1) mod 6).at n=9A202008
• The least number s having exactly n threes in the continued fraction of sqrt(s).at n=21A206583
• Interpolation polynomial through n points (0,1), (1,1), ..., (n-2,1) and (n-1,n) evaluated at 2n, a(0)=1.at n=7A237622
• Number of compositions of n, where the difference between the number of odd parts and the number of even parts is 7.at n=12A242505
• 29-gonal numbers: a(n) = n*(27*n-25)/2.at n=37A255187
• a(n) = greatest k such that A155043(k+A262509(n)) < A155043(A262509(n)).at n=47A262909
• Compound filter: a(n) = P(A046523(n), A161942(n)), where P(n,k) is sequence A000027 used as a pairing function.at n=63A286034
• Compound filter (prime signature & sum of the divisors): a(n) = P(A046523(n), A000203(n)), where P(n,k) is sequence A000027 used as a pairing function.at n=63A286360
• Anagrasum integers: integers N that exactly reproduce their set of digits when we form the set of sums of pairs of adjacent digits.at n=34A296521