Sequences

a(n) = a(n-1) + a(n-3), with a(0) = a(1) = 1, a(2) = 5.

Number of letters in n (in Spanish).

Days in year in proleptic Gregorian calendar.

a(n) = 3^(2^n) (or: write in base 3, read in base 9).

Period 4: repeat [0, 0, 0, 1].

Number of days in A.D. years from 100*n through 100*n + 99.

From studying monochromatic solutions to x3-x2=x2-x1+2n.

Number of Barlow packings that repeat after exactly n layers.

a(0) = 1, a(n+1) = 3 * a(n) - F(n)*(F(n) + 1), where F(n) = A000045(n) is n-th Fibonacci number.

Days per century for British calendar from first century, following Gregorian calendar after A.D. 1752.

Days per century for Roman calendar from first century, following Gregorian calendar after A.D. 1582.

Smallest number m such that m(m+1)/2 is divisible by n.

Variant of Carmichael's lambda function: a(p1^e1*...*pN^eN) = lcm((p1-1)*p1^(e1-1), ..., (pN-1)*pN^(eN-1)).

Nonprimes k that divide sigma(k) + phi(k).

Numbers k such that k divides phi(k) * sigma(k).

a(1) = 1; for n > 1, a(n) is defined by the property that n^a(n) divides n! but n^(a(n)+1) does not.

a(n) = least k>1 such that k^n divides k!.

Numbers k where A011776(k) grows.

Expansion of 1/((1-x)^3*(1-x^3)^2).

Expansion of 1/((1-2*x)^3*(1-x^2)^2).

Sextuple factorial numbers: a(n) = Product_{k=0..n-1} (6*k+3).

Coefficients of expansion of (1-x)/(1-2*x) in powers of x.

Duplicate of A001519.

Levine's sequence. First construct a triangle as follows. Row 1 is {1,1}; if row n is {r_1, ..., r_k} then row n+1 consists of {r_k 1's, r_{k-1} 2's, r_{k-2} 3's, etc.}; sequence consists of the final elements in each row.

Number of 3 X 3 matrices whose determinant is 1 mod n.

Number of 4 X 4 matrices whose determinant is 1 mod n.

Number of n X n matrices over Z_4 whose determinant is 1.

Number of n X n matrices whose determinant is 1 mod n.

Number of directed animals on a certain lattice.

Number of directed animals on a certain lattice.

Number of directed animals on a certain lattice.

Number of directed animals on a certain lattice.

Triangle of numbers of irreducible Euler sums.

Triangle defined by T(n+1, k) = T(n, k-1) + T(n-1, k), T(n,1) = 1, T(1,k) = 1, T(2,k) = min(2,k).

a(n) = floor(C(n,4)/5).

Number of irreducible alternating Euler sums of depth 6 and weight 6+2n.

a(n) = floor(C(n,6)/7).

Related to disproof of Gilbert-Pollak conjecture on n-dimensional Steiner minimal trees.

Duplicate of A006124.

Number of labeled forests of n nodes each component of which is a path.

Triangle read by rows, the inverse Bell transform of n!*binomial(4,n) (without column 0).

Duplicate of A007065.

Duplicate of A007625.

M-sequences from multicomplexes on at most 7 variables with no monomial of degree more than n-1.

M-sequences from multicomplexes on at most 8 variables with no monomial of degree more than n-1.

M-sequences from multicomplexes on at most 9 variables with no monomial of degree more than n-1.

M-sequences from multicomplexes on at most 10 variables with no monomial of degree more than n-1.

M-sequences from multicomplexes on at most 11 variables with no monomial of degree more than n-1.

M-sequences from multicomplexes on at most 12 variables with no monomial of degree more than n-1.

M-sequences from multicomplexes on 4 variables with all monomials of degree 2 but none of degree larger than n.