18209

Appears in sequences

• a(n) = (10n+1)*(10n+9).at n=13A001535
• Expansion of e.g.f.: exp(tan(tanh(x))).at n=10A009241
• tan(arcsin(x)-tanh(x))=3/3!*x^3-7/5!*x^5+497/7!*x^7+18209/9!*x^9...at n=3A013423
• a(n) is the smallest composite number c such that A002110(n) + c is prime.at n=31A038771
• Number of labeled T_0-hypergraphs with n distinct hyperedges (empty hyperedge excluded).at n=3A059089
• Sum of first n 6-almost primes.at n=33A086052
• a(n) = prime(n)*prime(n+2).at n=31A090076
• Composite members of sequence A138244.at n=4A138246
• 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, 0, 1), (-1, 1, 0), (0, -1, 1), (0, 0, 1), (1, 0, -1)}.at n=10A148321
• Number of permutations of 1..n containing the relative rank sequence { 236154 } at any spacing.at n=3A159149
• a(n) = prime(n) times the n-th nonnegative noncomposite.at n=33A176098
• Numbers k such that exactly three d in the range d <= k/2 exist which divide binomial(k-d-1,d-1) and which are not coprime to k.at n=19A178099
• a(n) = 2*a(n-1) + 5*a(n-2), a(0) = 1, a(1) = 3.at n=8A180168
• a(0)=0, a(1)=1, a(n)=(a(n-1) XOR n) + a(n-2).at n=20A182509
• 8th iteration of the hyperbinomial transform on the sequence of 1's.at n=4A218500
• S_5 sequence in partition of integers > 1 described in A240521.at n=38A240522
• Number of (n+2)X(4+2) 0..1 arrays with each 3X3 subblock having clockwise perimeter pattern 00000001 00000101 or 00010101.at n=4A260102
• Number of (n+2)X(5+2) 0..1 arrays with each 3X3 subblock having clockwise perimeter pattern 00000001 00000101 or 00010101.at n=3A260103
• T(n,k)=Number of (n+2)X(k+2) 0..1 arrays with each 3X3 subblock having clockwise perimeter pattern 00000001 00000101 or 00010101.at n=31A260106
• T(n,k)=Number of (n+2)X(k+2) 0..1 arrays with each 3X3 subblock having clockwise perimeter pattern 00000001 00000101 or 00010101.at n=32A260106