19147

Appears in sequences

• Number of compositions (p_1, p_2, p_3, ...) of n with 1 <= p_i <= i for all i.at n=17A008930
• Least inverse of A015910: smallest integer k > 0 such that 2^k mod k = n, or 0 if no such k exists.at n=5A036236
• Composite and every divisor (except 1) contains the digit 4.at n=11A062670
• Numbers n such that 2*n*k(n) is rational but not an integer, where k(n) is sum of successive remainders when computing the Euclidean algorithm for (1, 1/sqrt(n)) as defined in A086378 (MuPAD program is given there); numbers belonging to A086378 but not to A088900.at n=11A087414
• a(1) = 3, a(2) = 4. a(n) = (largest composite which occurs earlier in sequence) + (largest prime which occurs earlier in sequence).at n=31A120365
• Least positive number k such that 2^k mod k = 2n+1, or 0 if no such k exists.at n=2A124977
• Numbers k such that 2^k == 5 (mod k).at n=2A128121
• Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 1101-0111-0010 pattern in any orientation.at n=15A147243
• Define two triangular arrays by: B(0,0)=C(0,0)=1, B(0,r)=C(0,r)=0 for r>0, C(t,-1)=C(t,0); and for t,r >= 0, B(t+1,r)=C(t,r-1)+2C(t,r)-B(t,r), C(t+1,r)=B(t+1,r)+2B(t+1,r+1)-C(t,r). Sequence gives array B(t,r) read by rows.at n=49A177011
• Semiprimes p*q with p < q and 2^p (mod q) == 2^q (mod p).at n=25A179839
• The non-common part of the larger number of an amicable pair.at n=16A180327
• Triangle read by rows: the Fibonacci triangle times Pascal's triangle (A007318).at n=46A201166
• a(n) = [x^n] (1/(1 - x))*Product_{k>=1} 1/(1 - x^k)^n.at n=7A303070
• Regular triangle where T(n,k) is the number of non-isomorphic multiset partitions of k-element multiset partitions of multisets of size n.at n=41A330473
• Irregular triangle read by rows where T(n,k) is the number of integer compositions of n with k excedances (parts above the diagonal), all zeros removed.at n=55A352524
• Number of partitions p of n such that 5*min(p) is a part of p.at n=41A361459
• a(n) = Sum_{j=1..n} Sum_{k=1..n} phi(j*k).at n=19A372633