cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-10 of 26 results. Next

A248379 Even terms in A247665 in order of appearance.

Original entry on oeis.org

2, 4, 8, 14, 16, 32, 64, 128, 122, 244, 256, 512, 866, 1024, 1766, 2048, 4006, 4096, 8192, 8482, 12242, 16384, 32768, 52586, 65536, 105806, 131072
Offset: 1

Views

Author

N. J. A. Sloane, Oct 08 2014

Keywords

Comments

What are the terms that are not powers of 2?

Examples

			Table (extracted from Russ Cox's extended table in A247665) showing index where even numbers appear, the even number, and the number of different prime factors of that term:
3 4 1
7 8 1
15 14 2
31 16 1
63 32 1
127 64 1
255 128 1
511 122 2
1023 244 2
2047 256 1
4095 512 1
8191 866 2
16383 1024 1
32767 1766 2
65535 2048 1
131071 4006 2
262143 4096 1
524287 8192 1
1048575 8482 2
2097151 12242 2
4194303 16384 1
8388607 32768 1
16777215 52586 2
33554431 65536 1
67108863 105806 2
134217727 131072 1
...

References

Crossrefs

Cf. A247665, A248381, A248387, A248388.

Extensions

More terms from Russ Cox, Oct 11 2014

A248387 a(n) = index of n-th prime in A247665.

Original entry on oeis.org

1, 2, 4, 5, 8, 9, 10, 11, 12, 14, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 29, 30, 33, 34, 35, 36, 37, 38, 39, 41, 42, 43, 44, 45, 46, 47, 48, 49, 51, 52, 53, 54, 56, 58, 59, 60, 61, 62, 64, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81
Offset: 1

Views

Author

Russ Cox and N. J. A. Sloane, Oct 16 2014

Keywords

Links

Crossrefs

Cf. A247665, A248388, A248379.
Subsequence of A248918.

Programs

  • Haskell
    import Data.List (elemIndex); import Data.Maybe (fromJust)
a248387 = (+ 1) . fromJust . (`elemIndex` a247665_list) . a000040
-- Reinhard Zumkeller, Oct 16 2014

A248388 Indices of composite terms in A247665.

Original entry on oeis.org

3, 6, 7, 13, 15, 27, 28, 31, 32, 40, 50, 55, 57, 63, 65, 82, 101, 111, 112, 115, 116, 127, 131, 132, 165, 172, 203, 204, 223, 225, 231, 233, 255, 263, 264, 278, 331, 332, 358, 407, 408, 417, 447, 448, 451, 455, 463, 467, 511, 527, 557, 661, 663, 665, 717, 761
Offset: 1

Views

Author

Russ Cox and N. J. A. Sloane, Oct 16 2014

Keywords

Links

Crossrefs

Cf. A247665, A248387, A248379, A248390.

A248390 Composite terms in A247665 in order of appearance.

Original entry on oeis.org

4, 9, 8, 15, 14, 25, 27, 16, 49, 121, 169, 85, 57, 32, 161, 319, 403, 125, 289, 81, 361, 64, 259, 529, 451, 841, 559, 961, 235, 901, 177, 1159, 128, 343, 1369, 1541, 781, 1681, 2117, 1027, 1849, 2573, 445, 2209, 1649, 2809, 243, 1121, 122, 707
Offset: 1

Views

Author

Russ Cox and N. J. A. Sloane, Oct 16 2014

Keywords

Links

Crossrefs

Cf. A247665, A248388, A248391.

A248391 Terms in A247665 which are neither primes nor prime powers, in order of appearance.

Original entry on oeis.org

15, 14, 85, 57, 161, 319, 403, 259, 451, 559, 235, 901, 177, 1159, 1541, 781, 2117, 1027, 2573, 445, 1649, 1121, 122, 707, 851, 1133, 2911, 3103, 1417, 3397, 3503, 415, 4183, 2159, 5141, 393, 2603, 244, 973, 2323, 5513, 10117, 4223, 4553, 11899, 2171, 7439, 5549, 8507, 3247, 6731, 579, 2489, 8083, 1379, 3197
Offset: 1

Views

Author

Russ Cox and N. J. A. Sloane, Oct 16 2014

Keywords

Links

Crossrefs

Cf. A247665, A247885, A248379, A248387-A248390.

A248918 a(n) = index of (n+1)-th prime power in A247665.

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 6, 8, 9, 31, 10, 11, 12, 27, 28, 14, 16, 63, 17, 18, 19, 20, 32, 21, 22, 23, 127, 24, 25, 26, 29, 115, 30, 33, 34, 35, 36, 37, 38, 39, 40, 111, 41, 255, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 56, 58, 59, 60, 61, 62, 64, 66, 67
Offset: 1

Views

Author

Reinhard Zumkeller, Oct 16 2014

Keywords

Crossrefs

Cf. A248387 (subsequence), A000961.

Programs

  • Haskell
    import Data.List (elemIndex); import Data.Maybe (fromJust)
a248918 = (+ 1) . fromJust . (`elemIndex` a247665_list) . a000961 . (+ 1)

A249033 Lengths of successive runs of primes in A247665.

Original entry on oeis.org

2, 2, 5, 1, 11, 2, 7, 9, 4, 1, 5, 1, 16, 18, 9, 2, 10, 3, 32, 6, 30, 18, 1, 5, 1, 21, 7, 13, 52, 25, 48, 8, 29, 2, 3, 7, 3, 43, 15, 29, 103, 1, 1, 51, 43, 53, 1, 17, 59, 1, 5, 7, 15, 7, 86, 31, 59, 206, 3, 3, 102, 21, 65, 107, 2, 34, 118, 2, 10, 15, 30, 15
Offset: 1

Views

Author

N. J. A. Sloane, Oct 26 2014

Keywords

Links

Crossrefs

Cf. A247665.

Extensions

Typo in definition corrected by Arkadiusz Wesolowski, Nov 16 2014

A249049 a(0)=1; thereafter a(n) = number of integers 1 <= i < A247665(n) that are not yet terms of A247665.

Original entry on oeis.org

1, 1, 1, 1, 1, 2, 3, 2, 3, 4, 7, 8, 11, 10, 15, 14, 15, 20, 23, 24, 27, 32, 37, 38, 43, 46, 47, 46, 45, 50, 53, 52, 51, 56, 63, 66, 67, 70, 71, 74, 81, 86, 89, 94, 95, 104, 105, 110, 115, 118, 119, 122, 127, 128, 137, 136, 137, 136, 139, 140, 151, 162, 165, 164, 165
Offset: 0

Views

Author

N. J. A. Sloane, Oct 30 2014

Keywords

Comments

In short, the running count of missing terms in A247665.

Links

Crossrefs

Cf. A247665, A249050.

Programs

  • Maple
    # computes first M terms, assumes b1 is list of first M terms of A247665
M:=100; A:=[]; miss:=[1]; ctmiss:=[1]; last:=1; nom:=1;
for n from 1 to M do
t1:=b1[n]; A:=[op(A),t1];
if member(t1,miss) then nom:=nom-1; ctmiss:=[op(ctmiss),nom];
   miss:=remove('x->x=t1',miss);
else
   for i from last+1 to t1-1 do
   if not member(i,A) and not member(i,miss) then miss:=[op(miss),i]; nom:=nom+1; fi;
                             od:
   ctmiss:=[op(ctmiss),nom];
fi;
last:=t1;
od:
ctmiss;

A248381 Multiples of 3 in A247665 in order of appearance.

Original entry on oeis.org

9, 15, 27, 57, 81, 177, 243, 393, 579, 729, 849, 1257, 2187, 4197, 4143, 5853, 6561, 17817, 17781, 19683, 56157, 59049, 104289, 104277, 154509
Offset: 1

Views

Author

Russ Cox and N. J. A. Sloane, Oct 12 2014

Keywords

Comments

The initial multiples of 3 occur at positions 6,13,28,57,115,231, ... - conjecturally, for n > 13, A247665(n) is a multiple of 3 iff n = 29*2^k-1, k >= 0.

Examples

			Table showing index where multiples of 3 appear, the multiple of 3, and the number of different prime factors of that term:
6 9 1
13 15 2
28 27 1
57 57 2
115 81 1
231 177 2
463 243 1
927 393 2
1855 579 2
3711 729 1
7423 849 2
14847 1257 2
29695 2187 1
59391 4197 2
118783 4143 2
237567 5853 2
475135 6561 1
950271 17817 2
1900543 17781 2
3801087 19683 1
7602175 56157 2
15204351 59049 1
30408703 104289 2
60817407 104277 2
121634815 154509 2

Crossrefs

Cf. A247665, A248379 (multiples of 2).

A248389 Terms in A247665 that are less than the previous term.

Original entry on oeis.org

8, 15, 14, 25, 16, 85, 57, 32, 161, 403, 125, 81, 64, 259, 451, 559, 235, 901, 177, 1159, 128, 343, 781, 1027, 445, 1649, 243, 1121, 122, 707, 851, 1133, 2911, 3103, 1417, 3397, 3503, 415, 4183, 2159, 5141, 393, 2603, 244, 973, 2323, 10117, 1331, 4223, 4553, 11899, 2171, 6241, 5549, 625, 7921, 3247, 6731, 579
Offset: 1

Views

Author

Russ Cox and N. J. A. Sloane, Oct 16 2014

Keywords

Comments

All terms are composite.

Links

Crossrefs

Cf. A247665.
Showing 1-10 of 26 results. Next

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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