21400

Appears in sequences

• f-vectors for simplicial complexes of dimension at most 2 on at most n-1 vertices.at n=13A011827
• f-vectors for 9-neighborly simplicial complexes on n+8 vertices.at n=4A011841
• Otto Haxel's guess for magic numbers of nuclear shells.at n=40A033547
• Smallest integer >= 0 of the form x^3 - n^4.at n=27A070930
• If 0 <= n <= 3 then a(n) = n(n+1)(n+2)/3, if n >= 4 then a(n) = n(n^2+5)/3.at n=40A162626
• Lengths of runs of the initial digits of semiprimes in decimal representation, cf. A239634.at n=40A239639
• Number of (2+1) X (n+1) 0..1 arrays with every 2 X 2 subblock ne-sw antidiagonal difference nondecreasing horizontally and nw+se diagonal sum nondecreasing vertically.at n=31A258555
• a(n) = A002704(n)/2.at n=3A262570
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 131", based on the 5-celled von Neumann neighborhood.at n=31A270223
• Numbers that are not the difference of two binary palindromes (A006995).at n=44A290393
• Underline the central digit of all terms: the underlined digits reconstruct the starting sequence. This is also true if one translates the sequence in French and underlines the central letter of each word: the underlined letters spell the (French) sequence again. This is the lexicographically earliest sequence where repeated terms are admitted.at n=43A319718
• Underline the central digit of all terms: the underlined digits reconstruct the starting sequence. This is also true if one translates the sequence in French and underlines the central letter of each word: the underlined letters spell the (French) sequence again. This is the lexicographically earliest sequence of distinct terms.at n=43A319921
• a(n) = Sum_{k=1..n} k * rad(k).at n=42A350996
• G.f. A(x) satisfies 1/x = Sum_{n=-oo..+oo} A(x)^n * (1 + A(x)^n)^(n+1).at n=7A378264
• Conductor of elliptic curve y^2 = x^3 + n*x + n.at n=19A387834
• Expansion of g^2/(1 - x^2*g^6), where g = 1+x*g^4 is the g.f. of A002293.at n=6A391084