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.

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A062329 a(n) = (sum of digits of n) - (product of digits of n).

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 0, -1, -2, -3, -4, -5, -6, -7, 3, 1, -1, -3, -5, -7, -9, -11, -13, -15, 4, 1, -2, -5, -8, -11, -14, -17, -20, -23, 5, 1, -3, -7, -11, -15, -19, -23, -27, -31, 6, 1, -4, -9, -14, -19, -24, -29, -34, -39, 7, 1, -5, -11, -17, -23, -29, -35, -41, -47, 8, 1, -6, -13, -20, -27
Offset: 0

Views

Author

Amarnath Murthy, Jun 21 2001

Keywords

Examples

			a(23) = 2 + 3 - 2*3 = -1.
a(49) = -(4*9) + (4 + 9) = -36 + 13 = -23.
		

Crossrefs

Programs

  • Mathematica
    a[n_] := (t = IntegerDigits[n]; Plus @@ t - Times @@ t); Table[ a[n], {n, 0, 75}] (* Robert G. Wilson v *)

Extensions

Corrected and extended by Larry Reeves (larryr(AT)acm.org), Jun 22 2001
Signed version from Henry Bottomley, Jun 29 2001

A329761 Primes having only {1, 3, 9} as digits.

Original entry on oeis.org

3, 11, 13, 19, 31, 113, 131, 139, 191, 193, 199, 311, 313, 331, 911, 919, 991, 1193, 1319, 1399, 1913, 1931, 1933, 1993, 1999, 3119, 3191, 3313, 3319, 3331, 3391, 3911, 3919, 3931, 9133, 9199, 9311, 9319, 9391, 9931, 11113, 11119, 11131, 11311, 11393, 11399
Offset: 1

Views

Author

Alois P. Heinz, Nov 20 2019

Keywords

Comments

Original name was: Primes whose product of decimal digits is a power of 3.
Primes whose digit set is a subset of {1,3,9}.

Crossrefs

Subsequence of A030096.

Programs

  • Magma
    [p: p in PrimesUpTo(12000) | Set(Intseq(p)) subset [1,3,9]]; // Vincenzo Librandi, Jan 02 2019
  • Mathematica
    Select[Prime[Range[1500]],IntegerQ[Log[3,Times@@IntegerDigits[#]]]&] (* or *) Table[Select[FromDigits/@Tuples[{1,3,9},n],PrimeQ],{n,5}]// Flatten (* Harvey P. Dale, Dec 31 2019 *)

Formula

{ A000040 } intersect { A174813 }.
a(n) in { A000040 } and A007954(a(n)) in { A000244 }.

Extensions

Name changed by Sean A. Irvine, Jul 20 2025

A350181 Numbers of multiplicative persistence 2 which are themselves the product of digits of a number.

Original entry on oeis.org

25, 27, 28, 35, 36, 45, 48, 54, 56, 63, 64, 72, 84, 125, 126, 128, 135, 144, 162, 192, 216, 224, 225, 243, 245, 252, 256, 315, 324, 375, 432, 441, 512, 525, 567, 576, 588, 625, 675, 735, 756, 875, 945, 1125, 1134, 1152, 1176, 1215, 1225, 1296, 1323, 1372
Offset: 1

Views

Author

Daniel Mondot, Dec 18 2021

Keywords

Comments

The multiplicative persistence of a number mp(n) is the number of times the product of digits function p(n) must be applied to reach a single digit, i.e., A031346(n).
The product of digits function partitions all numbers into equivalence classes. There is a one-to-one correspondence between values in this sequence and equivalence classes of numbers with multiplicative persistence 3.
There are infinitely many numbers with mp of 1 to 11, but the classes of numbers (p(n)) are postulated to be finite for this and subsequent sequences A350182....
Equivalently:
This sequence consists of the numbers A007954(k) such that A031346(k) = 3,
These are the numbers k in A002473 such that A031346(k) = 2,
Or:
- they factor into powers of 2, 3, 5 and 7 exclusively.
- p(n) goes to a single digit in 2 steps.
Postulated to be finite and complete.
The largest known number is 2^25 * 3^227 * 7^28 (140 digits).
No more numbers have been found between 10^140 and probably 10^20000 (according to comment in A003001), and independently verified up to 10^10000.

Examples

			25 is in this sequence because:
- 25 goes to a single digit in 2 steps: p(25) = 10, p(10) = 0.
- 25 has ancestors 55, 155, etc. p(55) = 25.
27 is in this sequence because:
- 27 goes to a single digit in 2 steps: p(27) = 14, p(14) = 4.
- 27 has ancestors 39, 93, 333, 139, etc. p(39) = 27.
		

Crossrefs

Cf. A002473, A003001 (smallest number with multiplicative persistence n), A031346 (multiplicative persistence), A031347 (multiplicative digital root), A046511 (all numbers with mp of 2).
Cf. A350180, A350182, A350183, A350184, A350185, A350186, A350187 (numbers with mp 1, and 3 to 10 that are themselves 7-smooth numbers).

Programs

  • Mathematica
    Select[Range@1400,AllTrue[First/@FactorInteger@#,#<10&]&&Length@Most@NestWhileList[Times@@IntegerDigits@#&,#,#>9&]==2&] (* Giorgos Kalogeropoulos, Jan 16 2022 *)
  • Python
    from math import prod
    from sympy import factorint
    def pd(n): return prod(map(int, str(n)))
    def ok(n):
        if n <= 9 or max(factorint(n)) > 9: return False
        return (p := pd(n)) > 9 and pd(p) < 10
    print([k for k in range(1400) if ok(k)]) # Michael S. Branicky, Jan 16 2022

A350182 Numbers of multiplicative persistence 3 which are themselves the product of digits of a number.

Original entry on oeis.org

49, 75, 96, 98, 147, 168, 175, 189, 196, 288, 294, 336, 343, 392, 448, 486, 648, 672, 729, 784, 864, 882, 896, 972, 1344, 1715, 1792, 1944, 2268, 2744, 3136, 3375, 3888, 3969, 7938, 8192, 9375, 11664, 12288, 12348, 13824, 14336, 16384, 16464, 17496, 18144
Offset: 1

Views

Author

Daniel Mondot, Dec 18 2021

Keywords

Comments

The multiplicative persistence of a number mp(n) is the number of times the product of digits function p(n) must be applied to reach a single digit, i.e., A031346(n).
The product of digits function partitions all numbers into equivalence classes. There is a one-to-one correspondence between values in this sequence and equivalence classes of numbers with multiplicative persistence 4.
There are infinitely many numbers with mp of 1 to 11, but the classes of numbers (p(n)) are postulated to be finite for sequences A350181....
Equivalently:
This sequence consists of the numbers A007954(k) such that A031346(k) = 4,
These are the numbers k in A002473 such that A031346(k) = 3,
Or:
- they factor into powers of 2, 3, 5 and 7 exclusively.
- p(n) goes to a single digit in 3 steps.
Postulated to be finite and complete.
Let p(n) be the product of all the digits of n.
The multiplicative persistence of a number mp(n) is the number of times you need to apply p() to get to a single digit.
For example:
mp(1) is 0 since 1 is already a single-digit number.
mp(10) is 1 since p(10) = 0, and 0 is a single digit, 1 step.
mp(25) is 2 since p(25) = 10, p(10) = 0, 2 steps.
mp(96) is 3 since p(96) = 54, p(54) = 20, p(20) = 0, 3 steps.
mp(378) is 4 since p(378) = 168, p(168) = 48, p(48) = 32, p(32) = 6, 4 steps.
There are infinitely many numbers n such that mp(n)=4. But for each n with mp(n)=4, p(n) is a number included in this sequence, and this sequence is likely finite.
This sequence lists p(n) such that mp(n) = 4, or mp(p(n)) = 3.

Examples

			49 is in this sequence because:
- 49 goes to a single digit in 3 steps: p(49) = 36, p(36) = 18, p(18) = 8.
- p(77) = p(177) = p(717) = p(771) = 49, etc.
75 is in this sequence because:
- 75 goes to a single digit in 3 steps: p(75) = 35, p(35) = 15, p(15) = 5.
- p(355) = p(535) = p(1553) = 75, etc.
		

Crossrefs

Cf. A002473, A003001 (smallest number with multiplicative persistence n), A031346 (multiplicative persistence), A031347 (multiplicative digital root), A046512 (all numbers with mp of 3).
Cf. A350180, A350181, A350183, A350184, A350185, A350186, A350187 (numbers with mp 0, 1 and 3 to 10 that are themselves 7-smooth numbers).

A350183 Numbers of multiplicative persistence 4 which are themselves the product of digits of a number.

Original entry on oeis.org

378, 384, 686, 768, 1575, 1764, 2646, 4374, 6144, 6174, 6272, 7168, 8232, 8748, 16128, 21168, 23328, 27216, 28672, 32928, 34992, 49392, 59535, 67228, 77175, 96768, 112896, 139968, 148176, 163296, 214326, 236196, 393216, 642978, 691488, 774144, 777924
Offset: 1

Views

Author

Daniel Mondot, Dec 18 2021

Keywords

Comments

The multiplicative persistence of a number mp(n) is the number of times the product-of-digits function p(n) must be applied to reach a single digit, i.e., A031346(n).
The product-of-digits function partitions all numbers into equivalence classes. There is a one-to-one correspondence between values in this sequence and equivalence classes of numbers with multiplicative persistence 5.
There are infinitely many numbers with mp of 1 to 11, but the classes of numbers (p(n)) are postulated to be finite for sequences A350181....
Equivalently:
- This sequence lists all numbers A007954(k) such that A031346(k) = 5.
- These are the numbers k in A002473 such that A031346(k) = 4.
Or:
- These numbers factor into powers of 2, 3, 5 and 7 exclusively.
- p(n) goes to a single digit in 4 steps.
Postulated to be finite and complete.

Examples

			384 is in this sequence because:
- 384 goes to a single digit in 4 steps: p(384)=96, p(96)=54, p(54)=20, p(20)=0.
- p(886)=384, p(6248)=384, p(18816)=384, etc.
378 is in this sequence because:
- 378 goes to a single digits in 4 steps: p(378)=168, p(168)=48, p(48)=32, p(32)=6.
- p(679)=378, p(2397)=378, p(12379)=378, etc.
		

Crossrefs

Cf. A002473 (7-smooth), A003001 (smallest number with multiplicative persistence n), A031346 (multiplicative persistence), A031347 (multiplicative digital root), A046513 (all numbers with mp of 4).
Cf. A350180, A350181, A350182, A350184, A350185, A350186, A350187 (numbers with mp 1 to 3 and 5 to 10 that are themselves 7-smooth numbers).

Programs

  • Mathematica
    mx=10^6;lst=Sort@Flatten@Table[2^i*3^j*5^k*7^l,{i,0,Log[2,mx]},{j,0,Log[3,mx/2^i]},{k,0,Log[5,mx/(2^i*3^j)]},{l,0,Log[7,mx/(2^i*3^j*5^k)]}]; (* from A002473 *)
    Select[lst,Length@Most@NestWhileList[Times@@IntegerDigits@#&,#,#>9&]==4&] (* Giorgos Kalogeropoulos, Jan 16 2022 *)
  • PARI
    pd(n) = if (n, vecprod(digits(n)), 0); \\ A007954
    mp(n) = my(k=n, i=0); while(#Str(k) > 1, k=pd(k); i++); i; \\ A031346
    isok(k) = (mp(k)==4) && (vecmax(factor(k)[,1]) <= 7); \\ Michel Marcus, Jan 25 2022
  • Python
    from math import prod
    from sympy import factorint
    def pd(n): return prod(map(int, str(n)))
    def ok(n):
        if n <= 9 or max(factorint(n)) > 9: return False
        return (p := pd(n)) > 9 and (q := pd(p)) > 9 and (r := pd(q)) > 9 and pd(r) < 10
    print([k for k in range(778000) if ok(k)])
    

A350184 Numbers of multiplicative persistence 5 which are themselves the product of digits of a number.

Original entry on oeis.org

2688, 18816, 26244, 98784, 222264, 262144, 331776, 333396, 666792, 688128, 1769472, 2939328, 3687936, 4214784, 4917248, 13226976, 19361664, 38118276, 71663616, 111476736, 133413966, 161414428, 169869312, 184473632, 267846264, 368947264, 476171136, 1783627776
Offset: 1

Views

Author

Daniel Mondot, Dec 18 2021

Keywords

Comments

The multiplicative persistence of a number mp(n) is the number of times the product of digits function p(n) must be applied to reach a single digit, i.e., A031346(n).
The product of digits function partitions all numbers into equivalence classes. There is a one-to-one correspondence between values in this sequence and equivalence classes of numbers with multiplicative persistence 5.
There are infinitely many numbers with mp of 1 to 11, but the classes of numbers (p(n)) are postulated to be finite for sequences A350181....
Equivalently:
This sequence consists of all numbers A007954(k) such that A031346(k) = 6.
These are the numbers k in A002473 such that A031346(k) = 5.
Or:
- they factor into powers of 2, 3, 5 and 7 exclusively.
- p(n) goes to a single digit in 5 steps.
Postulated to be finite and complete.

Examples

			2688 is in this sequence because:
- 2688 goes to a single digit in 5 steps: p(2688)=768, p(768)=336, p(336)=54, p(54)=20, p(20)=0.
- p(27648) = p(47628) = 2688, etc.
331776 is in this sequence because:
- 331776 goes to a single digit in 5 steps: p(331776)=2646, p(2646)=288, p(288)=128, p(128)=16, p(16)=6.
- p(914838624) = p(888899) = 331776, etc.
		

Crossrefs

Intersection of A002473 and A046514 (all numbers with mp of 5).
Cf. A003001 (smallest number with multiplicative persistence n), A031346 (multiplicative persistence), A031347 (multiplicative digital root).
Cf. A350180, A350181, A350182, A350183, A350185, A350186, A350187 (numbers with mp 1 to 4 and 6 to 10 that are themselves 7-smooth numbers).

Programs

  • Mathematica
    mx=10^10;lst=Sort@Flatten@Table[2^i*3^j*5^k*7^l,{i,0,Log[2,mx]},{j,0,Log[3,mx/2^i]},{k,0,Log[5,mx/(2^i*3^j)]},{l,0,Log[7,mx/(2^i*3^j*5^k)]}];
    Select[lst,Length@Most@NestWhileList[Times@@IntegerDigits@#&,#,#>9&]==5&] (* code for 7-smooth numbers from A002473. - Giorgos Kalogeropoulos, Jan 16 2022 *)
  • Python
    from math import prod
    def hd(n):
        while (n&1) == 0:  n >>= 1
        while (n%3) == 0:  n /= 3
        while (n%5) == 0:  n /= 5
        while (n%7) == 0:  n /= 7
        return(n)
    def pd(n): return prod(map(int, str(n)))
    def ok(n):
        if hd(n) > 9: return False
        return (p := pd(n)) > 9 and (q := pd(p)) > 9 and (r := pd(q)) > 9 and (s := pd(r)) > 9 and pd(s) < 10
    print([k for k in range(10,476200000) if ok(k)])

A350185 Numbers of multiplicative persistence 6 which are themselves the product of digits of a number.

Original entry on oeis.org

27648, 47628, 64827, 84672, 134217728, 914838624, 1792336896, 3699376128, 48814981614, 134481277728, 147483721728, 1438916737499136
Offset: 1

Views

Author

Daniel Mondot, Jan 15 2022

Keywords

Comments

The multiplicative persistence of a number mp(n) is the number of times the product of digits function p(n) must be applied to reach a single digit, i.e., A031346(n).
The product of digits function partitions all numbers into equivalence classes. There is a one-to-one correspondence between values in this sequence and equivalence classes of numbers with multiplicative persistence 7.
There are infinitely many numbers with mp of 1 to 11, but the classes of numbers (p(n)) are postulated to be finite for sequences A350181....
Equivalently:
This sequence consists of the numbers A007954(k) such that A031346(k) = 7,
These are the numbers k in A002473 such that A031346(k) = 6,
Or:
- they factor into powers of 2, 3, 5 and 7 exclusively.
- p(n) goes to a single digit in 6 steps.
Postulated to be finite and complete.
a(13), if it exists, is > 10^20000, and likely > 10^80000.

Examples

			27648 is in sequence because:
- 27648 goes to a single digit in 6 steps: p(27648)=2688, p(2688)=768, p(768)=336, p(336)=54, p(54)=20, p(20)=0.
- p(338688) = p(168889) = 27648, etc.
		

Crossrefs

Cf. A002473, A003001 (smallest number with multiplicative persistence n), A031346 (multiplicative persistence), A031347 (multiplicative digital root), A046515 (all numbers with mp of 6).
Cf. A350180, A350181, A350182, A350183, A350184, A350186, A350187 (numbers with mp 1 to 5 and 7 to 10 that are themselves 7-smooth numbers).

Programs

  • Mathematica
    mx=10^16;lst=Sort@Flatten@Table[2^i*3^j*5^k*7^l,{i,0,Log[2,mx]},{j,0,Log[3,mx/2^i]},{k,0,Log[5,mx/(2^i*3^j)]},{l,0,Log[7,mx/(2^i*3^j*5^k)]}];
    Select[lst,Length@Most@NestWhileList[Times@@IntegerDigits@#&,#,#>9&]==6&] (* code for 7-smooth numbers from A002473. - Giorgos Kalogeropoulos, Jan 16 2022 *)
  • Python
    #this program may take 91 minutes to produce the first 8 members.
    from math import prod
    def hd(n):
        while (n&1) == 0:  n >>= 1
        while (n%3) == 0:  n /= 3
        while (n%5) == 0:  n /= 5
        while (n%7) == 0:  n /= 7
        return(n)
    def pd(n): return prod(map(int, str(n)))
    def ok(n):
        if hd(n) > 9: return False
        return (p := pd(n)) > 9 and (q := pd(p)) > 9 and (r := pd(q)) > 9 and (s := pd(r)) > 9 and (t := pd(s)) > 9 and pd(t) < 10
    print([k for k in range(10,3700000000) if ok(k)])

A350187 Numbers of multiplicative persistence 8 which are themselves the product of digits of a number.

Original entry on oeis.org

4478976, 784147392, 19421724672, 249143169618, 717233481216
Offset: 1

Views

Author

Daniel Mondot, Jan 30 2022

Keywords

Comments

The multiplicative persistence of a number mp(n) is the number of times the product of digits function p(n) must be applied to reach a single digit, i.e., A031346(n).
The product of digits function partitions all numbers into equivalence classes. There is a one-to-one correspondence between values in this sequence and equivalence classes of numbers with multiplicative persistence 9.
There are infinitely many numbers with mp of 1 to 11, but the classes of numbers (p(n)) are postulated to be finite for sequences A350181.
Equivalently:
This sequence consists of all numbers A007954(k) such that A031346(k) = 9.
They are the numbers k in A002473 such that A031346(k) = 8.
Or they factor into powers of 2, 3, 5 and 7 exclusively and p(n) goes to a single digit in 8 steps.
Postulated to be finite and complete.
a(6), if it exists, is > 10^20000, and likely > 10^171000.

Examples

			4478976 is in this sequence because:
- 4478976 goes to a single digit in 8 steps: 4478976 -> 338688 -> 27648 -> 2688 -> 768 -> 336 -> 54 -> 20 -> 0;
- p(438939648) = p(231928233984) = 4478976.
		

Crossrefs

Intersection of A002473 and A046517.
Cf. A003001 (smallest number with multiplicative persistence n), A031346 (multiplicative persistence), A031347 (multiplicative digital root), A046517 (all numbers with mp of 8).
Cf. A350180, A350181, A350182, A350183, A350184, A350185, A350186 (numbers with mp 1 to 7 and 9 to 10 that are themselves 7-smooth numbers).

A052423 Highest common factor of nonzero digits of n.

Original entry on oeis.org

1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 1, 3, 1, 1, 3, 1, 1, 3, 1, 1, 3, 4, 1, 2, 1, 4, 1, 2, 1, 4, 1, 5, 1, 1, 1, 1, 5, 1, 1, 1, 1, 6, 1, 2, 3, 2, 1, 6, 1, 2, 3, 7, 1, 1, 1, 1, 1, 1, 7, 1, 1, 8, 1, 2, 1, 4, 1, 2, 1, 8, 1, 9, 1, 1, 3, 1, 1, 3, 1, 1, 9, 1, 1, 1
Offset: 1

Views

Author

Henry Bottomley, Mar 17 2000

Keywords

Examples

			a(46) = 2 because the highest common factor of 4 and 6 is 2.
a(47) = 1 because the highest common factor of 4 and 7 is 1.
		

Crossrefs

Cf. A007954.

Programs

  • Haskell
    a052423 n = f n n where
       f x 1 = 1
       f x y | x < 10    = gcd x y
             | otherwise = if d == 1 then 1 else f x' (gcd d y)
             where (x', d) = divMod x 10
    -- Reinhard Zumkeller, Apr 14 2014
    
  • Maple
    a:= n-> igcd(subs(0=[][], convert(n, base, 10))[]):
    seq(a(n), n=1..100);  # Alois P. Heinz, Apr 04 2020
  • Mathematica
    Table[Apply[GCD, IntegerDigits[n]], {n, 100}] (* Alonso del Arte, Apr 02 2020 *)
  • PARI
    a(n) = my(d=digits(n)); gcd(select(x->(x!=0), d)); \\ Michel Marcus, Apr 04 2020
  • Scala
    def euclGCD(a: Int, b: Int): Int = b match { case 0 => a; case n => Math.abs(euclGCD(b, a % b)) }
    def digitGCD(n: Int) = n.toString.toCharArray.map( - 48).scanLeft(0)(euclGCD(, _)).last
    (1 to 100).map(digitGCD()) // _Alonso del Arte, Apr 02 2020
    

Formula

a(A069715(n)) = 1. - Reinhard Zumkeller, Apr 14 2014

A080464 Product of the two numbers formed by alternate digits of n.

Original entry on oeis.org

0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 0, 6, 12, 18, 24, 30, 36, 42, 48, 54, 0, 7, 14, 21, 28, 35, 42, 49, 56, 63, 0, 8, 16, 24, 32, 40, 48, 56, 64, 72, 0
Offset: 10

Views

Author

Amarnath Murthy, Mar 02 2003

Keywords

Examples

			a(132546) = 124 * 356 = 44144.
		

Crossrefs

Programs

  • Mathematica
    nad[n_]:=Module[{idn=IntegerDigits[n]},FromDigits[Take[idn,{1,-1,2}]] FromDigits[ Take[idn,{2,-1,2}]]]; Array[nad,120,10] (* Harvey P. Dale, Aug 07 2019 *)
  • PARI
    A080464(n,d=digits(n))={n=d*matrix(#d,2,z,s,if((z-s)%2,10^((#d-z)\2)));n[1]*n[2]}

Formula

a(n) < n for all n. - M. F. Hasler, Jan 10 2016

Extensions

More terms from Ray Chandler, Oct 11 2003
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