19872

Appears in sequences

• Form a triangle with n numbers in top row; all other numbers are the sum of their parents. E.g.: 4 1 2 7; 5 3 9; 8 12; 20. The numbers must be positive and distinct and the final number is to be minimized. Sequence gives final number.at n=12A028307
• Expansion of (theta_3(z^4)^3 + theta_2(z^4)^3)^3.at n=23A028696
• Base 9 digits are, in order, the first n terms of the periodic sequence with initial period 3,0,2.at n=4A037658
• Past of komet 'k2' (A038807).at n=8A038834
• Composite numbers k such that k - phi(k) divides sigma(k) - k.at n=12A068418
• Composite n such that n reduced mod(phi(n)) = sigma(n) reduced mod(n).at n=11A068495
• Integer quotient defining A068418 is 3.at n=4A069737
• Partial sums of n 3-spaced triangular numbers beginning with t(3), e.g., a(2) = t(3)+t(6) = 6+21 = 27.at n=22A085788
• Number of unimodal compositions of n+2 where the maximal part appears exactly twice.at n=27A114921
• First trisection of A028560.at n=46A147651
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 1), (0, 0, -1), (0, 1, 0), (1, 0, 1), (1, 1, 0)}.at n=7A151136
• Numbers with prime factorization pq^3r^5.at n=9A190011
• Phi(n) values in A115921.at n=33A216381
• G.f. A(x) satisfies: A(x) = x + x*[d/dx A(x)^2].at n=5A218222
• The greedy sequence of real numbers at least 1 that do not contain any 3-term geometric progressions with integer ratio.at n=21A235054
• Numbers such that the decimal digits of sigma(n) are a permutation of those of sigma(n)-n.at n=10A277114
• Number of set partitions of {1..n} where every block has the same average.at n=15A326512
• 3-admirable numbers: 3-abundant numbers (A068403) k such that exists a proper divisor d of k such that sigma(k) - 2*d = 3*k, where sigma(k) is the sum of divisors of k (A000203).at n=39A329189
• a(n) = r_4(n^2 + 1), where r_4(k) is the number of ways of writing k as a sum of 4 squares (A000118).at n=37A333173
• Composite numbers whose harmonic mean of their divisors that are larger than 1 is an integer.at n=24A335267