20845

Appears in sequences

• Number of partitions of n into parts not of the form 13k, 13k+4 or 13k-4. Also number of partitions with at most 3 parts of size 1 and differences between parts at distance 5 are greater than 1.at n=42A035952
• Numbers having four 5's in base 8.at n=5A043444
• Unicode codes for the Han digits.at n=6A061745
• a(n) = (2*n-1)*(n^2 -n +2)/2.at n=27A063488
• a(n) = a(n-1) + floor(a(n-2)/2) with a(0)=1, a(1)=2.at n=32A064324
• a(1) = 1, a(n+1) = a(n) + gpf(Sum_{i=1..n} a(i)), where gpf=A006530 (greatest prime factor).at n=18A080182
• Number of partitions of n such that the least part occurs at least twice.at n=37A117989
• Ulam's spiral (WSW spoke).at n=36A143854
• Number of partitions of n where the difference between consecutive parts is at most 8.at n=38A238868
• Number of partitions of n such that m(greatest part) <= m(1), where m = multiplicity.at n=38A240077
• Composite numbers equal to the sum of the prime factors, with multiplicity, of the previous k numbers, for some k.at n=11A257525
• Numbers equal to the sum of the prime factors, with multiplicity, of the previous k numbers, for some k.at n=15A257976
• Relative of Hofstadter Q-sequence: a(n) = max(0, n+20830) for n <= 0; a(n) = a(n-a(n-1)) + a(n-a(n-2)) + a(n-a(n-3)) for n > 0.at n=19A283887
• Number of permutations p of [n] such that the up-down signature of 0,p has nonnegative partial sums with a maximal value of nine.at n=3A316396
• Number of compositions (ordered partitions) of n into centered heptagonal numbers (A069099).at n=51A322803
• Odd composite integers m such that U(m)^2 == 1 (mod m) and V(m) == 5 (mod m), where U(m)=A004254(m) and V(m)=A003501(m) are the m-th generalized Lucas and Pell-Lucas numbers of parameters a=5 and b=1, respectively.at n=38A337779