19780

Appears in sequences

• a(n) = s(1)s(n) + s(2)s(n-1) + ... + s(k)s(n-k+1), where k = [ n/2 ], s = (1, p(1), p(2), ...).at n=29A025099
• Dirichlet convolution of 3^(n-1) with phi(n).at n=9A034754
• Denominators of continued fraction convergents to sqrt(758).at n=9A042461
• Number of partitions of n with equal number of even and odd parts.at n=53A045931
• Numbers in ascending order formed by using all the digits of the next n numbers.at n=30A081991
• Numbers n such that sigma(n) = 6*phi(n).at n=7A104900
• Pentagonal numbers (A000326) whose digit reversal is a semiprime (A001358).at n=34A115709
• Pentagonal numbers that are the sum of a nonzero pentagonal number and a nonzero square in at least one way.at n=42A134938
• Number of 5-step one space at a time bishop's tours on an n X n board summed over all starting positions.at n=16A187158
• Number of -n..n arrays x(0..3) of 4 elements with zero sum and no two consecutive zero elements.at n=14A199531
• a(n) = denominator(B°(2*n))/4 where the B°(n) are Zagier's modified Bernoulli numbers.at n=21A216912
• Numbers k such that gcd(sigma(k), phi(k)) (A009223) attains record values.at n=23A222711
• Expansion of Product_{k>=1} 1/(1 - x^(2*k+1))^(2*k+1).at n=28A263199
• Irregular table read by rows: n-th row lists the 9 n-gonal numbers of a 3 X 3 semimagic square with the smallest magic sum. The terms of each row are arranged in the manner shown in A261816.at n=26A265141
• Number of 3Xn integer arrays with each element equal to the number of horizontal and antidiagonal neighbors equal to itself.at n=19A266013
• Pisot sequence E(31,51), a(n)=[a(n-1)^2/a(n-2)+1/2].at n=13A275628
• Decimal representation of the diagonal from the corner to the origin of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 358", based on the 5-celled von Neumann neighborhood.at n=36A287784
• Decimal representation of the diagonal from the corner to the origin of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 358", based on the 5-celled von Neumann neighborhood.at n=37A287784
• Least positive integer m such that m*n divides F(m+n), where F(k) denotes the k-th Fibonacci number A000045(k).at n=19A297573
• Pentagonal numbers divisible by 4.at n=29A298397