The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A165401 Antidiagonally reading the array, formed via: first, writing the primes in the first row (row_1), and forming all successive rows' elements using the previous rows' elements as: row_2(j) = row_1(j)*row_1(j+1) - row_1(j) - row_1(j+1), and so on. The first 'column' of the array, 2 1 -1 -1 -1 -1 -1 -1 ... is converted to its absolute value. 0
 2, 1, 3, 1, 7, 5, 1, 131, 23, 7, 1, 165619, 1275, 59, 11, 1, 1443643414307, 8716707, 6843, 119, 13, 1, 1930155333520916730618052608, 1337002832135523, 153383955, 22419, 191, 17, 1 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The actual array that leads to the list given above is: 2 3 5 7 11 13 17 19 ... 1 7 23 59 119 191 287 395 ... 1 131 1275 6843 22419 54339 112683 241915 ... 1 165619 8716707 ... 1 1443643414307 ... It can be observed that: 1) Obviously, all primes will appear in the list at least once, as the first row of the generating array is composed of all the primes. 2) There exist primes that appear more than once (e.g., 23, 59, 131, 191...). 3) When we have two successive primes in a row, prime(i) & prime(i+1) -as in all of the first row, and occasionally in other rows- the element just below these two is, obviously, Euler_tot( prime(i) * prime (i+1) ) - 1. LINKS CROSSREFS Cf. A000040: The list of prime numbers is the first row of the array, that is converted to the list. Cf. A037165: This list, "Prime(n)*prime(n+1)-prime(n)-prime(n+1)" is the second row of the array, that is converted to the list. Sequence in context: A191854 A129646 A277640 * A319916 A213074 A140966 Adjacent sequences:  A165398 A165399 A165400 * A165402 A165403 A165404 KEYWORD nonn,tabl AUTHOR Umut Uludag, Sep 17 2009 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 29 00:42 EST 2022. Contains 350670 sequences. (Running on oeis4.)