28141

Appears in sequences

• a(n) = a(n-1) + a(n - 1 minus the number of terms of a(k) == (mod 5) so far).at n=31A060732
• Semiprimes in A054556.at n=23A113693
• Number of 1..13 integer arrays v[1..n] of length n with all autocorrelation values sum(i){v[i]*v[i-k]} distinct for k in 0..n-1.at n=3A171287
• Number of 1..n integer arrays v[1..4] of length 4 with all autocorrelation values sum(i){v[i]*v[i-k]} distinct for k in 0..3.at n=12A171341
• Number of n-bead necklaces labeled with numbers -2..2 allowing reversal, with sum zero and avoiding the patterns z z+1 z+2 and z z-1 z-2.at n=9A209479
• Number of (w,x,y,z) with all terms in {1,...,n} and w<2x+y+z.at n=13A212145
• Numbers k such that k^3 - b2 is a triangular number (A000217), where b2 is the largest square less than k^3.at n=38A233401
• a(n) = prime(n) * prime(2n).at n=27A319613
• Nonprime Heinz numbers of multiples of triangular partitions, or of finite arithmetic progressions with offset 0.at n=36A325407
• Sum of sums of omegas of the parts over all strict integer partitions of n.at n=49A325515
• Number of integer partitions of n whose length is a semi-sum of the parts.at n=43A367394
• a(n) = the smallest positive integer that produces a product that contains the digit 2 when multiplied by 2 at most n times, and where a further multiplication by 2 produces a number that does not contain the digit 2. Set a(n) = -1 if no such number exists.at n=17A381183